diff --git a/packages/utils/src/functions/getHashFragment.ts b/packages/utils/src/functions/getHashFragment.ts
index b4ffb67..2e7664c 100644
--- a/packages/utils/src/functions/getHashFragment.ts
+++ b/packages/utils/src/functions/getHashFragment.ts
@@ -7,6 +7,7 @@ import { isString } from './isString'
  *
  * @param url
  * @returns {string}
+ * @throws {URIError} 内部で利用している `decodeURIComponent()` がエラーをスローする可能性がある
  * @example
  * // 返値: hash fragment
  * getHashFragment('https://localhost:8080?test=32#hash+fragment')
diff --git a/packages/utils/src/functions/getQueryString.ts b/packages/utils/src/functions/getQueryString.ts
index 10011a2..4d873d3 100644
--- a/packages/utils/src/functions/getQueryString.ts
+++ b/packages/utils/src/functions/getQueryString.ts
@@ -7,6 +7,7 @@ import { removeHashFragment } from './removeHashFragment'
  *
  * @param url
  * @returns {string}
+ * @throws {URIError} 内部で利用している `decodeURIComponent()` がエラーをスローする可能性がある
  * @example
  * // 返値: ?test1=32&test2=ア
  * getQueryString('https://localhost:8080?test1=32&test2=%E3%82%A2#fragment')
diff --git a/packages/utils/src/functions/safeDecodeURIComponent.ts b/packages/utils/src/functions/safeDecodeURIComponent.ts
new file mode 100644
index 0000000..1d463c7
--- /dev/null
+++ b/packages/utils/src/functions/safeDecodeURIComponent.ts
@@ -0,0 +1,28 @@
+/**
+ * decodeURIComponent()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返却する
+ *
+ * @param value
+ * @returns {{ data: string; error: null } | { data: null; error: URIError }}
+ * @example
+ * const { data, error } = safeDecodeURIComponent('foo%20bar') // => { data: 'foo bar', error: null }
+ * if (error) {
+ *  console.error(error)
+ * } else {
+ *   console.log(data) // => 'foo bar'
+ * }
+ */
+export function safeDecodeURIComponent(value: string): { data: string; error: null } | { data: null; error: URIError } {
+  try {
+    const data = decodeURIComponent(value)
+    return { data, error: null }
+  } catch (e) {
+    return {
+      data: null,
+      /**
+       * try中で発生する例外はdecodeURIComponentの仕様によるものなので、SyntaxErrorでアサーションしている
+       * @see {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURIComponent#exceptions}
+       */
+      error: e as URIError,
+    }
+  }
+}
diff --git a/packages/utils/src/functions/safeEncodeURIComponent.ts b/packages/utils/src/functions/safeEncodeURIComponent.ts
new file mode 100644
index 0000000..df9c599
--- /dev/null
+++ b/packages/utils/src/functions/safeEncodeURIComponent.ts
@@ -0,0 +1,28 @@
+/**
+ * encodeURIComponent()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返却する
+ *
+ * @param value
+ * @returns {{ data: string; error: null } | { data: null; error: URIError }}
+ * @example
+ * const { data, error } = safeEncodeURIComponent('foo bar') // => { data: 'foo%20bar', error: null }
+ * if (error) {
+ *   console.error(error)
+ * } else {
+ *   console.log(data) // => 'foo%20bar'
+ * }
+ */
+export function safeEncodeURIComponent(value: string): { data: string; error: null } | { data: null; error: URIError } {
+  try {
+    const data = encodeURIComponent(value)
+    return { data, error: null }
+  } catch (e) {
+    return {
+      data: null,
+      /**
+       * try中で発生する例外はencodeURIComponentの仕様によるものなので、SyntaxErrorでアサーションしている
+       * @see {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent#exceptions}
+       */
+      error: e as SyntaxError,
+    }
+  }
+}
diff --git a/packages/utils/src/functions/safeJsonParse.ts b/packages/utils/src/functions/safeJsonParse.ts
new file mode 100644
index 0000000..6fb8db9
--- /dev/null
+++ b/packages/utils/src/functions/safeJsonParse.ts
@@ -0,0 +1,36 @@
+/**
+ * JSON.parse()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返す
+ *
+ * 型変数 `T` はJSON.parse()でパースするデータの型を指定する
+ *
+ * ※ ただし、型ガードは行わないため、呼び出し元で型ガードを適宜実施すること
+ *
+ * @param value
+ * @param options
+ * @returns {{ data: T; error: null } | { data: null; error: SyntaxError }}
+ * @example
+ * const { data, error } = safeJsonParse<{ foo: string }>('{"foo": "bar"}') // => { data: { foo: 'bar' }, error: null }
+ * if (error) {
+ *   console.error(error)
+ * } else {
+ *   console.log(data) // => { foo: 'bar' }
+ * }
+ */
+export function safeJsonParse<T>(
+  value: string,
+  options?: { reviver?: Parameters<typeof JSON.parse>[1] }
+): { data: T; error: null } | { data: null; error: SyntaxError } {
+  try {
+    const data = JSON.parse(value, options?.reviver)
+    return { data, error: null }
+  } catch (e) {
+    return {
+      data: null,
+      /**
+       * try中で発生する例外はJSON.parseの仕様によるものなので、SyntaxErrorでアサーションしている
+       * @see {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse#exceptions}
+       */
+      error: e as SyntaxError,
+    }
+  }
+}
diff --git a/packages/utils/src/functions/safeJsonStringify.ts b/packages/utils/src/functions/safeJsonStringify.ts
new file mode 100644
index 0000000..0bfdff3
--- /dev/null
+++ b/packages/utils/src/functions/safeJsonStringify.ts
@@ -0,0 +1,35 @@
+/**
+ * JSON.stringify()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返す
+ *
+ * @param value
+ * @param options
+ * @returns {{ data: string; error: null } | { data: null; error: TypeError }}
+ * @example
+ * const { data, error } = safeJsonStringify({ foo: 'bar' }) // => { data: '{"foo":"bar"}', error: null }
+ * if (error) {
+ *   console.error(error)
+ * } else {
+ *   console.log(data) // => '{"foo":"bar"}'
+ * }
+ */
+export function safeJsonStringify<T>(
+  value: T,
+  options?: {
+    replacer?: Parameters<typeof JSON.stringify>[1]
+    space?: Parameters<typeof JSON.stringify>[2]
+  }
+): { data: string; error: null } | { data: null; error: TypeError } {
+  try {
+    const data = JSON.stringify(value, options?.replacer, options?.space)
+    return { data, error: null }
+  } catch (e) {
+    return {
+      data: null,
+      /**
+       * try中で発生する例外はJSON.stringifyの仕様によるものなので、TypeErrorでアサーションしている
+       * @see {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#exceptions}
+       */
+      error: e as TypeError,
+    }
+  }
+}
diff --git a/packages/utils/src/index.ts b/packages/utils/src/index.ts
index bbcfea2..5a85ea7 100644
--- a/packages/utils/src/index.ts
+++ b/packages/utils/src/index.ts
@@ -39,6 +39,10 @@ export * from './functions/replaceHwAlphanumericsWithFw'
 export * from './functions/replaceNewLineChars'
 export * from './functions/replaceSpacesWithTab'
 export * from './functions/replaceTabWithSpaces'
+export * from './functions/safeDecodeURIComponent'
+export * from './functions/safeEncodeURIComponent'
+export * from './functions/safeJsonParse'
+export * from './functions/safeJsonStringify'
 export * from './functions/separateArray'
 export * from './functions/strf'
 export * from './functions/withRootRelativePath'
diff --git a/packages/utils/src/types/utils.ts b/packages/utils/src/types/utils.ts
index 24c6294..5b9874a 100644
--- a/packages/utils/src/types/utils.ts
+++ b/packages/utils/src/types/utils.ts
@@ -126,3 +126,21 @@ export type ExactNotMatchTypeKeys<T, U> = keyof Omit<T, ExactMatchTypeKeys<T, U>
 export type RequiredAtLeastOne<T, K extends keyof T = keyof T> = Pick<T, Exclude<keyof T, K>> &
   Partial<Pick<T, K>> &
   (K extends keyof T ? { [_K in K]-?: Pick<Required<T>, _K> }[K] : never)
+
+/**
+ * オブジェクトの全フィールドの型からundefined,nullを除外した型を得る
+ *
+ * ※ ネストしたオブジェクトのフィールドに対しては適用されない
+ *
+ * @example
+ * type Post = {
+ *   id: `post_${number}`
+ *   title: string
+ *   body: string | undefined
+ *   author: { name: string; age: number | undefined }
+ *   createdAt: Date
+ *   updatedAt?: Date | null
+ * }
+ * type NewPost = NonNullishFields<Post> // { id: `post_${number}`; title: string; body: string; author: { name: string; age: number | undefined }; createdAt: Date; updatedAt: Date }
+ */
+export type NonNullishFields<T extends {}> = { [K in keyof T]-?: NonNullable<T[K]> }
diff --git a/packages/utils/tests/functions/getHashFragment.spec.ts b/packages/utils/tests/functions/getHashFragment.spec.ts
index fc30084..c8a102a 100644
--- a/packages/utils/tests/functions/getHashFragment.spec.ts
+++ b/packages/utils/tests/functions/getHashFragment.spec.ts
@@ -1,4 +1,4 @@
-import { test, expect } from 'vitest'
+import { expect, test } from 'vitest'
 import { getHashFragment } from '../../src'
 
 test('getHashFragment()', () => {
@@ -8,4 +8,5 @@ test('getHashFragment()', () => {
   expect(getHashFragment('https://localhost:8080?test=32#hash_fragment')).toBe('hash_fragment')
   expect(getHashFragment('https://localhost:8080?test=32#hash+fragment')).toBe('hash fragment')
   expect(getHashFragment('https://localhost:8080?test=32#%E3%83%86%E3%82%B9%E3%83%88')).toBe('テスト')
+  expect(() => getHashFragment('https://localhost:8080?test=32#%E0%A4%A')).toThrowError(URIError)
 })
diff --git a/packages/utils/tests/functions/getQueryString.spec.ts b/packages/utils/tests/functions/getQueryString.spec.ts
index 4ce1664..9651131 100644
--- a/packages/utils/tests/functions/getQueryString.spec.ts
+++ b/packages/utils/tests/functions/getQueryString.spec.ts
@@ -1,4 +1,4 @@
-import { test, expect } from 'vitest'
+import { expect, test } from 'vitest'
 import { getQueryString } from '../../src'
 
 test('getQueryString()', () => {
@@ -8,4 +8,5 @@ test('getQueryString()', () => {
   expect(getQueryString('https://localhost:8080?#test1=3+2&test2=%E3%82%A2')).toBe('?')
   expect(getQueryString('https://localhost:8080#?test1=3+2&test2=%E3%82%A2')).toBe('')
   expect(getQueryString('https://localhost:8080/#?test1=32&test2=%E3%82%A2')).toBe('')
+  expect(() => getQueryString('https://localhost:8080/?test1=32&test2=%E0%A4%A')).toThrowError(URIError)
 })
diff --git a/packages/utils/tests/functions/safeDecodeURIComponent.spec.ts b/packages/utils/tests/functions/safeDecodeURIComponent.spec.ts
new file mode 100644
index 0000000..3ad8ee2
--- /dev/null
+++ b/packages/utils/tests/functions/safeDecodeURIComponent.spec.ts
@@ -0,0 +1,16 @@
+import { describe, expect, test } from 'vitest'
+import { safeDecodeURIComponent } from '../../src'
+
+describe('safeDecodeURIComponent()', () => {
+  test('デコードされた値が返ってくる', () => {
+    expect(safeDecodeURIComponent('%3Fx%3Dtest')).toEqual({ data: '?x=test', error: null })
+    expect(safeDecodeURIComponent('foo%20bar')).toEqual({ data: 'foo bar', error: null })
+    expect(safeDecodeURIComponent('%E3%83%86%E3%82%B9%E3%83%88')).toEqual({ data: 'テスト', error: null })
+  })
+
+  test('URIErrorが返ってくる', () => {
+    const { data, error } = safeDecodeURIComponent('%')
+    expect(data).toBeNull()
+    expect(error).toBeInstanceOf(URIError)
+  })
+})
diff --git a/packages/utils/tests/functions/safeEncodeURIComponent.spec.ts b/packages/utils/tests/functions/safeEncodeURIComponent.spec.ts
new file mode 100644
index 0000000..d163fc8
--- /dev/null
+++ b/packages/utils/tests/functions/safeEncodeURIComponent.spec.ts
@@ -0,0 +1,16 @@
+import { describe, expect, test } from 'vitest'
+import { safeEncodeURIComponent } from '../../src'
+
+describe('safeEncodeURIComponent()', () => {
+  test('エンコードされた値が返ってくる', () => {
+    expect(safeEncodeURIComponent('?x=test')).toEqual({ data: '%3Fx%3Dtest', error: null })
+    expect(safeEncodeURIComponent('foo bar')).toEqual({ data: 'foo%20bar', error: null })
+    expect(safeEncodeURIComponent('テスト')).toEqual({ data: '%E3%83%86%E3%82%B9%E3%83%88', error: null })
+  })
+
+  test('URIErrorが返ってくる', () => {
+    const { data, error } = safeEncodeURIComponent('\uD800')
+    expect(data).toBeNull()
+    expect(error).toBeInstanceOf(URIError)
+  })
+})
diff --git a/packages/utils/tests/functions/safeJsonParse.spec.ts b/packages/utils/tests/functions/safeJsonParse.spec.ts
new file mode 100644
index 0000000..9173d95
--- /dev/null
+++ b/packages/utils/tests/functions/safeJsonParse.spec.ts
@@ -0,0 +1,34 @@
+import { describe, expect, test } from 'vitest'
+import { safeJsonParse } from '../../src'
+
+describe('safeJsonParse()', () => {
+  describe('パースに成功する', () => {
+    test('optionsなし', () => {
+      const jsonString = '{"foo": "bar"}'
+      const { data, error } = safeJsonParse<{ foo: string }>(jsonString)
+      expect(data).toEqual({ foo: 'bar' })
+      expect(error).toBeNull()
+    })
+
+    test('options.reviverあり', () => {
+      const jsonString = '{"foo": "bar"}'
+      const { data, error } = safeJsonParse<{ foo: string }>(jsonString, {
+        reviver: (key, value) => {
+          if (key === 'foo') {
+            return `${value}!`
+          }
+          return value
+        },
+      })
+      expect(data).toEqual({ foo: 'bar!' })
+      expect(error).toBeNull()
+    })
+  })
+
+  test('パースに失敗する', () => {
+    const jsonString = '{"foo": "bar"'
+    const { data, error } = safeJsonParse(jsonString)
+    expect(data).toBeNull()
+    expect(error).toBeInstanceOf(SyntaxError)
+  })
+})
diff --git a/packages/utils/tests/functions/safeJsonStringify.spec.ts b/packages/utils/tests/functions/safeJsonStringify.spec.ts
new file mode 100644
index 0000000..41db837
--- /dev/null
+++ b/packages/utils/tests/functions/safeJsonStringify.spec.ts
@@ -0,0 +1,65 @@
+import { describe, expect, test } from 'vitest'
+import { safeJsonStringify } from '../../src'
+
+describe('safeJsonStringify()', () => {
+  describe('文字列化に成功する', () => {
+    test('optionsなし', () => {
+      const { data, error } = safeJsonStringify({ foo: 'bar' })
+      expect(data).toBe('{"foo":"bar"}')
+      expect(error).toBeNull()
+    })
+
+    test('options.replacerあり (関数のケース)', () => {
+      const target = { foo: 'bar', hoo: 3, goo: true }
+      const { data, error } = safeJsonStringify(target, {
+        // @ts-ignore: 問題ないので型エラーを無視
+        replacer: (key: keyof typeof target, value: (typeof target)[keyof typeof target]) => {
+          if (key === 'foo') {
+            return `${value}!`
+          }
+          if (key === 'hoo' && typeof value === 'number') {
+            return value * 2
+          }
+          return value
+        },
+      })
+      expect(data).toBe('{"foo":"bar!","hoo":6,"goo":true}')
+      expect(error).toBeNull()
+    })
+
+    test('options.replacerあり (配列のケース)', () => {
+      const target = { foo: 'bar', hoo: 3, goo: true, 3: 'three' }
+      const { data, error } = safeJsonStringify(target, {
+        replacer: ['foo', 'hoo', 3],
+      })
+      expect(data).toBe('{"foo":"bar","hoo":3,"3":"three"}')
+      expect(error).toBeNull()
+    })
+
+    test('options.spaceあり (数値のケース)', () => {
+      const target = { foo: 'bar' }
+      const { data, error } = safeJsonStringify(target, {
+        space: 2,
+      })
+      expect(data).toBe('{\n  "foo": "bar"\n}')
+      expect(error).toBeNull()
+    })
+
+    test('options.spaceあり (文字のケース)', () => {
+      const target = { foo: 'bar' }
+      const { data, error } = safeJsonStringify(target, {
+        space: '\t',
+      })
+      expect(data).toBe('{\n\t"foo": "bar"\n}')
+      expect(error).toBeNull()
+    })
+  })
+
+  test('文字列化に失敗する', () => {
+    // BigInt は JSON.stringify で文字列化できないので例外が発生する
+    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#exceptions
+    const { data, error } = safeJsonStringify({ bigint: 2n })
+    expect(data).toBeNull()
+    expect(error).toBeInstanceOf(TypeError)
+  })
+})
diff --git a/packages/utils/tests/types/utils.spec.ts b/packages/utils/tests/types/utils.spec.ts
index ac46a01..82ab831 100644
--- a/packages/utils/tests/types/utils.spec.ts
+++ b/packages/utils/tests/types/utils.spec.ts
@@ -1,9 +1,10 @@
-import { expectTypeOf, describe, test } from 'vitest'
+import { describe, expectTypeOf, test } from 'vitest'
 import type {
-  MatchTypeKeys,
   ExactMatchTypeKeys,
-  NotMatchTypeKeys,
   ExactNotMatchTypeKeys,
+  MatchTypeKeys,
+  NonNullishFields,
+  NotMatchTypeKeys,
   RequiredAtLeastOne,
 } from '../../src'
 
@@ -113,4 +114,26 @@ describe('types/utils.ts', () => {
       expectTypeOf({}).not.toEqualTypeOf<Test>()
     })
   })
+
+  test('NonNullishFields', () => {
+    expectTypeOf<
+      NonNullishFields<{
+        id: `post_${number}`
+        title: string
+        body: string | undefined
+        author: { name: string; age: number | undefined }
+        createdAt: Date
+        updatedAt?: Date | null
+      }>
+    >().toEqualTypeOf<{
+      id: `post_${number}`
+      title: string
+      body: string
+      author: { name: string; age: number | undefined }
+      createdAt: Date
+      updatedAt: Date
+    }>()
+
+    expectTypeOf<NonNullishFields<string>>().toEqualTypeOf<string>()
+  })
 })
diff --git a/website/packages/utils/functions/getHashFragment.md b/website/packages/utils/functions/getHashFragment.md
index 2191ff4..be1f430 100644
--- a/website/packages/utils/functions/getHashFragment.md
+++ b/website/packages/utils/functions/getHashFragment.md
@@ -7,24 +7,28 @@ custom_edit_url: null
 
 **getHashFragment**(`url`): `string`
 
-引数urlにあるフラグメントを削除したものを返却
+引数 url にあるフラグメントを削除したものを返却
 
 ※ 文字列中に含まれる `+` (プラス記号)は半角スペースに変換されます
 
+**`Throws`**
+
+内部で利用している `decodeURIComponent()` がエラーをスローする可能性がある
+
 **`Example`**
 
 ```ts
 // 返値: hash fragment
-getHashFragment('https://localhost:8080?test=32#hash+fragment')
+getHashFragment("https://localhost:8080?test=32#hash+fragment");
 
 // 返値: テスト
-getHashFragment('https://localhost:8080?test=32#%E3%83%86%E3%82%B9%E3%83%88')
+getHashFragment("https://localhost:8080?test=32#%E3%83%86%E3%82%B9%E3%83%88");
 ```
 
 ## Parameters
 
-| Name | Type |
-| :------ | :------ |
+| Name  | Type              |
+| :---- | :---------------- |
 | `url` | `string` \| `URL` |
 
 ## Returns
diff --git a/website/packages/utils/functions/getQueryString.md b/website/packages/utils/functions/getQueryString.md
index 5db823d..d6c3845 100644
--- a/website/packages/utils/functions/getQueryString.md
+++ b/website/packages/utils/functions/getQueryString.md
@@ -7,27 +7,31 @@ custom_edit_url: null
 
 **getQueryString**(`url`): `string`
 
-引数urlのクエリパラメータ部分を返却
+引数 url のクエリパラメータ部分を返却
 
 ※ 文字列中に含まれる `+` (プラス記号)は半角スペースに変換されます
 
+**`Throws`**
+
+内部で利用している `decodeURIComponent()` がエラーをスローする可能性がある
+
 **`Example`**
 
 ```ts
 // 返値: ?test1=32&test2=ア
-getQueryString('https://localhost:8080?test1=32&test2=%E3%82%A2#fragment')
+getQueryString("https://localhost:8080?test1=32&test2=%E3%82%A2#fragment");
 
 // 返値: ?test1=32&test2=ア
-getQueryString('/path/to/?test1=32&test2=%E3%82%A2#fragment')
+getQueryString("/path/to/?test1=32&test2=%E3%82%A2#fragment");
 
 // 返値: ?test1=3 2&test2=ア
-getQueryString('https://localhost:8080?test1=3+2&test2=%E3%82%A2#fragment')
+getQueryString("https://localhost:8080?test1=3+2&test2=%E3%82%A2#fragment");
 ```
 
 ## Parameters
 
-| Name | Type |
-| :------ | :------ |
+| Name  | Type     |
+| :---- | :------- |
 | `url` | `string` |
 
 ## Returns
diff --git a/website/packages/utils/functions/safeDecodeURIComponent.md b/website/packages/utils/functions/safeDecodeURIComponent.md
new file mode 100644
index 0000000..c263a66
--- /dev/null
+++ b/website/packages/utils/functions/safeDecodeURIComponent.md
@@ -0,0 +1,31 @@
+---
+id: "safe-decode-uri-component"
+title: "safeDecodeURIComponent"
+sidebar_label: "safeDecodeURIComponent"
+custom_edit_url: null
+---
+
+**safeDecodeURIComponent**(`value`): \{ `data`: `string` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `URIError` }
+
+decodeURIComponent()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返却する
+
+**`Example`**
+
+```ts
+const { data, error } = safeDecodeURIComponent("foo%20bar"); // => { data: 'foo bar', error: null }
+if (error) {
+  console.error(error);
+} else {
+  console.log(data); // => 'foo bar'
+}
+```
+
+## Parameters
+
+| Name    | Type     |
+| :------ | :------- |
+| `value` | `string` |
+
+## Returns
+
+\{ `data`: `string` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `URIError` }
diff --git a/website/packages/utils/functions/safeEncodeURIComponent.md b/website/packages/utils/functions/safeEncodeURIComponent.md
new file mode 100644
index 0000000..3e3a29b
--- /dev/null
+++ b/website/packages/utils/functions/safeEncodeURIComponent.md
@@ -0,0 +1,31 @@
+---
+id: "safe-encode-uri-component"
+title: "safeEncodeURIComponent"
+sidebar_label: "safeEncodeURIComponent"
+custom_edit_url: null
+---
+
+**safeEncodeURIComponent**(`value`): \{ `data`: `string` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `URIError` }
+
+encodeURIComponent()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返却する
+
+**`Example`**
+
+```ts
+const { data, error } = safeEncodeURIComponent("foo bar"); // => { data: 'foo%20bar', error: null }
+if (error) {
+  console.error(error);
+} else {
+  console.log(data); // => 'foo%20bar'
+}
+```
+
+## Parameters
+
+| Name    | Type     |
+| :------ | :------- |
+| `value` | `string` |
+
+## Returns
+
+\{ `data`: `string` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `URIError` }
diff --git a/website/packages/utils/functions/safeJsonParse.md b/website/packages/utils/functions/safeJsonParse.md
new file mode 100644
index 0000000..3829385
--- /dev/null
+++ b/website/packages/utils/functions/safeJsonParse.md
@@ -0,0 +1,39 @@
+---
+id: "safe-json-parse"
+title: "safeJsonParse"
+sidebar_label: "safeJsonParse"
+custom_edit_url: null
+---
+
+**safeJsonParse**\<`T`\>(`value`, `options?`): \{ `data`: `T` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `SyntaxError` }
+
+JSON.parse()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返す
+
+型変数 `T` は JSON.parse()でパースするデータの型を指定する
+
+※ ただし、型ガードは行わないため、呼び出し元で型ガードを適宜実施すること
+
+**`Example`**
+
+```ts
+const { data, error } = safeJsonParse<{ foo: string }>('{"foo": "bar"}'); // => { data: { foo: 'bar' }, error: null }
+if (error) {
+  console.error(error);
+} else {
+  console.log(data); // => { foo: 'bar' }
+}
+```
+
+## Parameters
+
+| Name               | Type     |
+| :----------------- | :------- |
+| `value`            | `string` |
+| `options?`         | `Object` |
+| `options.reviver?` | _※1_     |
+
+- _※1_ https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse#reviver に従う
+
+## Returns
+
+\{ `data`: `T` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `SyntaxError` }
diff --git a/website/packages/utils/functions/safeJsonStringify.md b/website/packages/utils/functions/safeJsonStringify.md
new file mode 100644
index 0000000..4259d46
--- /dev/null
+++ b/website/packages/utils/functions/safeJsonStringify.md
@@ -0,0 +1,37 @@
+---
+id: "safe-json-stringify"
+title: "safeJsonStringify"
+sidebar_label: "safeJsonStringify"
+custom_edit_url: null
+---
+
+**safeJsonStringify**\<`T`\>(`value`, `options?`): \{ `data`: `string` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `TypeError` }
+
+JSON.stringify()で発生する例外をキャッチして、例外が発生した場合はエラーオブジェクトを返す
+
+**`Example`**
+
+```ts
+const { data, error } = safeJsonStringify({ foo: "bar" }); // => { data: '{"foo":"bar"}', error: null }
+if (error) {
+  console.error(error);
+} else {
+  console.log(data); // => '{"foo":"bar"}'
+}
+```
+
+## Parameters
+
+| Name                | Type     |
+| :------------------ | :------- |
+| `value`             | `T`      |
+| `options?`          | `Object` |
+| `options.replacer?` | _※1_     |
+| `options.space?`    | _※2_     |
+
+- _※1_ https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#replacer に従う
+- _※2_ https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#space に従う
+
+## Returns
+
+\{ `data`: `T` ; `error`: `null` } \| \{ `data`: `null` ; `error`: `SyntaxError` }
diff --git a/website/packages/utils/types/NonNullishFields.md b/website/packages/utils/types/NonNullishFields.md
new file mode 100644
index 0000000..b579c91
--- /dev/null
+++ b/website/packages/utils/types/NonNullishFields.md
@@ -0,0 +1,25 @@
+---
+id: "non-nullish-fields"
+title: "NonNullishFields"
+sidebar_label: "NonNullishFields"
+custom_edit_url: null
+---
+
+オブジェクトの全フィールドの型から undefined,null を除外した型を得る
+
+※ ネストしたオブジェクトのフィールドに対しては適用されない
+
+**`Example`**
+
+```ts
+type Post = {
+  id: `post_${number}`;
+  title: string;
+  body: string | undefined;
+  author: { name: string; age: number | undefined };
+  createdAt: Date;
+  updatedAt?: Date | null;
+};
+// NewPost => { id: `post_${number}`; title: string; body: string; author: { name: string; age: number | undefined }; createdAt: Date; updatedAt: Date }
+type NewPost = NonNullishFields<Post>;
+```