diff --git a/ChangeLog.md b/ChangeLog.md
index 46c1065..1744a4e 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+### v1.2.1 / 2024-02-25
+
+  - String の非推奨のメソッドを変更: substr() → slice()
+
 ## v1.2.0 / 2024-02-03
 
   - #5 麻雀サーバーに関する処理を追加
diff --git a/lib/board.js b/lib/board.js
index f888a39..8b1665e 100644
--- a/lib/board.js
+++ b/lib/board.js
@@ -86,7 +86,7 @@ module.exports = class Board {
         this.lunban = dapai.l;
         this.shoupai[dapai.l].dapai(dapai.p, false);
         this.he[dapai.l].dapai(dapai.p);
-        this._lizhi = dapai.p.substr(-1) == '*';
+        this._lizhi = dapai.p.slice(-1) == '*';
     }
 
     fulou(fulou) {
diff --git a/lib/game.js b/lib/game.js
index 74c7364..268e6c9 100644
--- a/lib/game.js
+++ b/lib/game.js
@@ -72,7 +72,7 @@ module.exports = class Game {
     }
 
     say(name, l) {
-        if (this._view) this._view.say(name, l); 
+        if (this._view) this._view.say(name, l);
     }
 
     stop(callback = ()=>{}) {
@@ -298,12 +298,12 @@ module.exports = class Game {
 
         if (this._diyizimo) {
             if (! dapai.match(/^z[1234]/))  this._fengpai = false;
-            if (this._dapai && this._dapai.substr(0,2) != dapai.substr(0,2))
+            if (this._dapai && this._dapai.slice(0,2) != dapai.slice(0,2))
                                             this._fengpai = false;
         }
         else                                this._fengpai = false;
 
-        if (dapai.substr(-1) == '*') {
+        if (dapai.slice(-1) == '*') {
             this._lizhi[model.lunban] = this._diyizimo ? 2 : 1;
             this._yifa[model.lunban]  = this._rule['一発あり'];
         }
@@ -448,8 +448,8 @@ module.exports = class Game {
         let menfeng  = this._hule.length ? this._hule.shift() : model.lunban;
         let rongpai  = menfeng == model.lunban ? null
                      : (this._hule_option == 'qianggang'
-                            ? this._gang[0] + this._gang.substr(-1)
-                            : this._dapai.substr(0,2)
+                            ? this._gang[0] + this._gang.slice(-1)
+                            : this._dapai.slice(0,2)
                        ) + '_+=-'[(4 + model.lunban - menfeng) % 4];
         let shoupai  = model.shoupai[menfeng].clone();
         let fubaopai = shoupai.lizhi ? model.shan.fubaopai : null;
@@ -728,7 +728,7 @@ module.exports = class Game {
         else if (reply.dapai) {
             let dapai = reply.dapai.replace(/\*$/,'');
             if (this.get_dapai().find(p => p == dapai)) {
-                if (reply.dapai.substr(-1) == '*' && this.allow_lizhi(dapai)) {
+                if (reply.dapai.slice(-1) == '*' && this.allow_lizhi(dapai)) {
                     this.say('lizhi', model.lunban);
                     return this.delay(()=>this.dapai(reply.dapai));
                 }
@@ -770,7 +770,7 @@ module.exports = class Game {
             return this.delay(()=>this.hule());
         }
 
-        if (this._dapai.substr(-1) == '*') {
+        if (this._dapai.slice(-1) == '*') {
             model.defen[model.player_id[model.lunban]] -= 1000;
             model.lizhibang++;
 
@@ -872,7 +872,7 @@ module.exports = class Game {
                 this._hule.push(l);
             }
             else {
-                let p = this._gang[0] + this._gang.substr(-1);
+                let p = this._gang[0] + this._gang.slice(-1);
                 let shoupai = model.shoupai[l].clone().zimo(p);
                 if (Majiang.Util.xiangting(shoupai) == -1)
                                                 this._neng_rong[l] = false;
@@ -969,7 +969,7 @@ module.exports = class Game {
         }
         else {
             let p = (this._status == 'gang'
-                        ? this._gang[0] + this._gang.substr(-1)
+                        ? this._gang[0] + this._gang.slice(-1)
                         : this._dapai
                     ) + '_+=-'[(4 + model.lunban - l) % 4];
             let hupai = model.shoupai[l].lizhi
diff --git a/lib/he.js b/lib/he.js
index 5ade8e2..e654e9e 100644
--- a/lib/he.js
+++ b/lib/he.js
@@ -23,7 +23,7 @@ module.exports = class He {
         if (! Majiang.Shoupai.valid_mianzi(m))      throw new Error(m);
         let p = m[0] + m.match(/\d(?=[\+\=\-])/), d = m.match(/[\+\=\-]/);
         if (! d)                                    throw new Error(m);
-        if (this._pai[this._pai.length - 1].substr(0,2) != p)
+        if (this._pai[this._pai.length - 1].slice(0,2) != p)
                                                     throw new Error(m);
         this._pai[this._pai.length - 1] += d;
         return this;
diff --git a/lib/hule.js b/lib/hule.js
index 4e63d71..682ec7f 100644
--- a/lib/hule.js
+++ b/lib/hule.js
@@ -116,7 +116,7 @@ function hule_mianzi_qidui(shoupai, hulepai) {
         for (let n = 1; n < bingpai.length; n++) {
             if (bingpai[n] == 0) continue;
             if (bingpai[n] == 2) {
-                let m = (s+n == hulepai.substr(0,2))
+                let m = (s+n == hulepai.slice(0,2))
                             ? s+n+n + hulepai[2] + '!'
                             : s+n+n;
                 mianzi.push(m);
@@ -140,14 +140,14 @@ function hule_mianzi_guoshi(shoupai, hulepai) {
         let nn = (s == 'z') ? [1,2,3,4,5,6,7] :[1,9];
         for (let n of nn) {
             if (bingpai[n] == 2) {
-                let m = (s+n == hulepai.substr(0,2))
+                let m = (s+n == hulepai.slice(0,2))
                             ? s+n+n + hulepai[2] + '!'
                             : s+n+n;
                 mianzi.unshift(m);
                 n_duizi++;
             }
             else if (bingpai[n] == 1) {
-                let m = (s+n == hulepai.substr(0,2))
+                let m = (s+n == hulepai.slice(0,2))
                             ? s+n + hulepai[2] + '!'
                             : s+n;
                 mianzi.push(m);
@@ -177,7 +177,7 @@ function hule_mianzi_jiulian(shoupai, hulepai) {
         }
     }
     if (mianzi.length != 14) return [];
-    mianzi += hulepai.substr(1) + '!';
+    mianzi += hulepai.slice(1) + '!';
 
     return [ [mianzi] ];
 }
@@ -684,7 +684,7 @@ function hule(shoupai, rongpai, param) {
 
     if (rongpai) {
         if (! rongpai.match(/[\+\=\-]$/)) throw new Error(rongpai);
-        rongpai = rongpai.substr(0,2) + rongpai.substr(-1);
+        rongpai = rongpai.slice(0,2) + rongpai.slice(-1);
     }
 
     let max;
diff --git a/lib/index.js b/lib/index.js
index f44e5f6..6eaa890 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,5 +1,5 @@
 /*!
- *  @kobalab/majiang-core v1.2.0
+ *  @kobalab/majiang-core v1.2.1
  *
  *  Copyright(C) 2021 Satoshi Kobayashi
  *  Released under the MIT license
diff --git a/lib/player.js b/lib/player.js
index f569bbc..767c438 100644
--- a/lib/player.js
+++ b/lib/player.js
@@ -115,7 +115,7 @@ module.exports = class Player {
 
         this._diyizimo = false;
         if (gang.l != this._menfeng && ! gang.m.match(/^[mpsz]\d{4}$/)) {
-            let s = gang.m[0], n = +gang.m.substr(-1)||5;
+            let s = gang.m[0], n = +gang.m.slice(-1)||5;
             if (this.hulepai.find(p=> p == s+n)) this._neng_rong = false;
         }
     }
diff --git a/lib/shoupai.js b/lib/shoupai.js
index fb6e849..3ebcd4f 100644
--- a/lib/shoupai.js
+++ b/lib/shoupai.js
@@ -84,7 +84,7 @@ module.exports = class Shoupai {
         }
 
         shoupai._zimo  = shoupai._zimo || zimo || null;
-        shoupai._lizhi = bingpai.substr(-1) == '*';
+        shoupai._lizhi = bingpai.slice(-1) == '*';
 
         return shoupai;
     }
@@ -194,7 +194,7 @@ module.exports = class Shoupai {
         let s = p[0], n = +p[1];
         this.decrease(s, n);
         this._zimo = null;
-        if (p.substr(-1) == '*') this._lizhi = true;
+        if (p.slice(-1) == '*') this._lizhi = true;
         return this;
     }
 
@@ -224,11 +224,11 @@ module.exports = class Shoupai {
             this._fulou.push(m);
         }
         else if (m.match(/\d{3}[\+\=\-]\d$/)) {
-            let m1 = m.substr(0,5);
+            let m1 = m.slice(0,5);
             let i = this._fulou.findIndex(m2 => m1 == m2);
             if (i < 0)                              throw new Error([this, m]);
             this._fulou[i] = m;
-            this.decrease(s, m.substr(-1));
+            this.decrease(s, m.slice(-1));
         }
         else                                        throw new Error([this, m]);
         this._zimo = null;
@@ -381,7 +381,7 @@ module.exports = class Shoupai {
                     else {
                         if (this._lizhi) continue;
                         for (let m of this._fulou) {
-                            if (m.replace(/0/g,'5').substr(0,4) == s+n+n+n) {
+                            if (m.replace(/0/g,'5').slice(0,4) == s+n+n+n) {
                                 if (n == 5 && bingpai[0] > 0) mianzi.push(m+0);
                                 else                          mianzi.push(m+n);
                             }
diff --git a/package-lock.json b/package-lock.json
index d915ba6..6924545 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@kobalab/majiang-core",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "@kobalab/majiang-core",
-      "version": "1.2.0",
+      "version": "1.2.1",
       "license": "MIT",
       "devDependencies": {
         "mocha": "^10.2.0",
diff --git a/package.json b/package.json
index 628aa0a..1586272 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@kobalab/majiang-core",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "麻雀基本ライブラリ",
   "publishConfig": {
     "access": "public"