diff --git a/README.md b/README.md
index 0faad283..ad57361e 100644
--- a/README.md
+++ b/README.md
@@ -23,7 +23,7 @@ For Next.js, see https://github.com/kitsuyui/nextjs-playground/ .
       https://www.npmjs.com/package/@kitsuyui/react-clock
 - [x] `@kitsuyui/react-timer` ... [![npm version](https://badge.fury.io/js/@kitsuyui%2Freact-timer.svg)](https://badge.fury.io/js/@kitsuyui%2Freact-timer)
       https://www.npmjs.com/package/@kitsuyui/react-timer
-- [ ] Stopwatch
+- [x] `@kitsuyui/react-stopwatch` ... [![npm version](https://badge.fury.io/js/@kitsuyui%2Freact-stopwatch.svg)](https://badge.fury.io/js/@kitsuyui%2Freact-stopwatch)
 - [ ] Alarm
 - [ ] Dice
 
diff --git a/packages/stopwatch/README.md b/packages/stopwatch/README.md
index 4d6e2ecf..5b4a6992 100644
--- a/packages/stopwatch/README.md
+++ b/packages/stopwatch/README.md
@@ -1 +1,55 @@
 # @kitsuyui/react-stopwatch
+
+[![npm version](https://badge.fury.io/js/@kitsuyui%2Freact-stopwatch.svg)](https://badge.fury.io/js/@kitsuyui%2Freact-stopwatch)
+
+<img width="204" alt="Stopwatch" src="https://github.com/kitsuyui/react-playground/assets/2596972/b25cc228-24ce-45eb-850a-c3775b708d3d">
+
+## Installation
+
+### npm
+
+```sh
+npm install @kitsuyui/react-stopwatch
+```
+
+### yarn
+
+```sh
+yarn add @kitsuyui/react-stopwatch
+```
+
+## Usage
+
+```tsx
+import { StopWatchContainer, MinimalStopwatch } from '@kitsuyui/react-stopwatch'
+
+const Stopwatch = () => {
+  return (
+    <StopwatchContainer>
+      <StopwatchContext.Consumer>
+        {(props: StopwatchProps) => <MinimalStopwatch {...props} />}
+      </StopwatchContext.Consumer>
+    </StopwatchContainer>
+  )
+}
+```
+
+StopwatchContainer is a component that provides StopwatchContext.
+Stopwatchs are pure components that do not depend on StopwatchContext. Accept StopwatchProps as props.
+So you can define your own Stopwatch component by same interface.
+
+```typescript
+export interface StopwatchValue {
+  elapsedTime: number
+  running: boolean
+}
+
+export interface StopwatchActions {
+  start(): void
+  stop(): void
+  toggle(): void
+  reset(): void
+}
+
+export type StopwatchProps = StopwatchValue & StopwatchActions
+```