diff --git a/Cargo.lock b/Cargo.lock
index da5f6ff..39e7705 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -940,7 +940,6 @@ dependencies = [
 name = "font_rasterizer"
 version = "0.1.0"
 dependencies = [
- "anyhow",
  "bezier_converter",
  "bitflags 2.6.0",
  "bytemuck",
@@ -960,6 +959,7 @@ dependencies = [
  "rustybuzz",
  "stroke_parser",
  "text_buffer",
+ "thiserror 2.0.9",
  "unicode-width 0.2.0",
  "wasm-bindgen",
  "wasm-bindgen-futures",
diff --git a/font_rasterizer/Cargo.toml b/font_rasterizer/Cargo.toml
index a9db434..72acf78 100644
--- a/font_rasterizer/Cargo.toml
+++ b/font_rasterizer/Cargo.toml
@@ -9,7 +9,7 @@ crate-type = ["cdylib", "rlib"]
 
 [dependencies]
 cfg-if = { workspace = true }
-anyhow = { workspace = true }
+thiserror = { workspace = true }
 env_logger = { workspace = true }
 log = { workspace = true }
 wgpu = { workspace = true }
diff --git a/font_rasterizer/src/errors.rs b/font_rasterizer/src/errors.rs
new file mode 100644
index 0000000..3093f77
--- /dev/null
+++ b/font_rasterizer/src/errors.rs
@@ -0,0 +1,21 @@
+use rustybuzz::ttf_parser::GlyphId;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum FontRasterizerError {
+    #[error("glyph not found. char: {0}")]
+    GlyphNotFound(char),
+    #[error("glyph index not found")]
+    GlyphIndexNotFound,
+    // バッファの確保に失敗しているエラー
+    #[error("Failed to allocate buffer. kind: {0:?}")]
+    BufferAllocationFailed(BufferKind),
+    #[error("outline glyph is failed. glyph_id:{0:?}")]
+    NoOutlineGlyph(GlyphId),
+}
+
+#[derive(Debug)]
+pub enum BufferKind {
+    Vertex,
+    Index,
+}
diff --git a/font_rasterizer/src/font_buffer.rs b/font_rasterizer/src/font_buffer.rs
index 1685672..83bf774 100644
--- a/font_rasterizer/src/font_buffer.rs
+++ b/font_rasterizer/src/font_buffer.rs
@@ -4,8 +4,6 @@ use std::{
     sync::Arc,
 };
 
-use anyhow::Context;
-
 use font_collector::FontData;
 use log::{debug, info};
 use text_buffer::editor::CharWidthResolver;
@@ -13,6 +11,7 @@ use wgpu::BufferUsages;
 
 use crate::{
     char_width_calcurator::{CharWidth, CharWidthCalculator},
+    errors::{BufferKind, FontRasterizerError},
     font_converter::{FontVertexConverter, GlyphVertex, GlyphVertexData, Vertex},
 };
 
@@ -151,11 +150,15 @@ impl GlyphVertexBuffer {
         }
     }
 
-    pub(crate) fn draw_info(&self, c: &char, direction: &Direction) -> anyhow::Result<DrawInfo> {
+    pub(crate) fn draw_info(
+        &self,
+        c: &char,
+        direction: &Direction,
+    ) -> Result<DrawInfo, FontRasterizerError> {
         let index = &self
             .buffer_index
             .get(c)
-            .with_context(|| format!("get char from buffer index. c:{}", c))?
+            .ok_or(FontRasterizerError::GlyphIndexNotFound)?
             .get_entry(direction);
 
         let vertex_buffer = &self.vertex_buffers[index.vertex_buffer_index];
@@ -199,7 +202,7 @@ impl GlyphVertexBuffer {
         device: &wgpu::Device,
         queue: &wgpu::Queue,
         chars: HashSet<char>,
-    ) -> anyhow::Result<()> {
+    ) -> Result<(), FontRasterizerError> {
         // 既にバッファに登録済みの char は除外する。
         let chars = chars
             .into_iter()
@@ -253,16 +256,20 @@ impl GlyphVertexBuffer {
         queue: &wgpu::Queue,
         c: char,
         glyph_data: GlyphVertexData,
-    ) -> anyhow::Result<BufferIndex> {
+    ) -> Result<BufferIndex, FontRasterizerError> {
         self.ensure_buffer_capacity(device, queue, &glyph_data);
 
         let vertex_buffer_index = self
             .appendable_vertex_buffer_index(glyph_data.vertex_size())
-            .with_context(|| "fail ensure vertex_buffer")?;
+            .ok_or(FontRasterizerError::BufferAllocationFailed(
+                BufferKind::Vertex,
+            ))?;
 
         let index_buffer_index = self
             .appendable_index_buffer_index(glyph_data.index_size())
-            .with_context(|| "fail ensure index_buffer")?;
+            .ok_or(FontRasterizerError::BufferAllocationFailed(
+                BufferKind::Index,
+            ))?;
 
         // buffer に書き込むキューを登録する
         let vertex_buffer = self.vertex_buffers.get_mut(vertex_buffer_index).unwrap();
diff --git a/font_rasterizer/src/font_converter.rs b/font_rasterizer/src/font_converter.rs
index 90d67e5..e59d0d1 100644
--- a/font_rasterizer/src/font_converter.rs
+++ b/font_rasterizer/src/font_converter.rs
@@ -1,6 +1,5 @@
 use std::sync::Arc;
 
-use anyhow::Context;
 use bezier_converter::CubicBezier;
 use font_collector::FontData;
 use log::debug;
@@ -10,7 +9,9 @@ use rustybuzz::{
     Direction, Face, UnicodeBuffer,
 };
 
-use crate::{char_width_calcurator::CharWidth, debug_mode::DEBUG_FLAGS};
+use crate::{
+    char_width_calcurator::CharWidth, debug_mode::DEBUG_FLAGS, errors::FontRasterizerError,
+};
 
 pub(crate) struct FontVertexConverter {
     fonts: Arc<Vec<FontData>>,
@@ -28,7 +29,7 @@ impl FontVertexConverter {
             .collect::<Vec<Face>>()
     }
 
-    fn get_face_and_glyph_ids(&self, c: char) -> anyhow::Result<(Face, CharGlyphIds)> {
+    fn get_face_and_glyph_ids(&self, c: char) -> Result<(Face, CharGlyphIds), FontRasterizerError> {
         let mut buf = UnicodeBuffer::new();
         buf.set_direction(Direction::TopToBottom);
         buf.add(c, 0);
@@ -51,10 +52,14 @@ impl FontVertexConverter {
                 ));
             }
         }
-        anyhow::bail!("no glyph. char:{}", c)
+        Err(FontRasterizerError::GlyphNotFound(c))
     }
 
-    pub(crate) fn convert(&self, c: char, width: CharWidth) -> anyhow::Result<GlyphVertex> {
+    pub(crate) fn convert(
+        &self,
+        c: char,
+        width: CharWidth,
+    ) -> Result<GlyphVertex, FontRasterizerError> {
         let (
             face,
             CharGlyphIds {
@@ -169,10 +174,10 @@ impl GlyphVertexBuilder {
         glyph_id: GlyphId,
         width: CharWidth,
         face: &Face,
-    ) -> anyhow::Result<GlyphVertexData> {
+    ) -> Result<GlyphVertexData, FontRasterizerError> {
         let rect = face
             .outline_glyph(glyph_id, &mut self)
-            .with_context(|| format!("ougline glyph is afiled. glyph_id:{:?}", glyph_id))?;
+            .ok_or(FontRasterizerError::NoOutlineGlyph(glyph_id))?;
 
         let global = face.global_bounding_box();
         let global_width = global.width() as f32;
diff --git a/font_rasterizer/src/lib.rs b/font_rasterizer/src/lib.rs
index 7114f4c..0ef3f0b 100644
--- a/font_rasterizer/src/lib.rs
+++ b/font_rasterizer/src/lib.rs
@@ -3,6 +3,7 @@ pub mod char_width_calcurator;
 pub mod color_theme;
 pub mod context;
 mod debug_mode;
+pub mod errors;
 pub mod font_buffer;
 pub mod font_converter;
 pub mod instances;