diff --git a/packages/smarthr-ui/src/components/Textarea/Textarea.stories.tsx b/packages/smarthr-ui/src/components/Textarea/Textarea.stories.tsx
index dc2fc14f24..c7b062e9c3 100644
--- a/packages/smarthr-ui/src/components/Textarea/Textarea.stories.tsx
+++ b/packages/smarthr-ui/src/components/Textarea/Textarea.stories.tsx
@@ -14,9 +14,9 @@ export default {
 }
 
 const Template: StoryFn = () => {
-  const [value, setValue] = useState('message👌')
-  const onChangeValue = (e: React.ChangeEvent<HTMLTextAreaElement>) =>
-    setValue(e.currentTarget.value)
+  const [value1, setValue1] = useState('message👌')
+  const [value2, setValue2] = useState('message👌')
+  const [value3, setValue3] = useState('message👌')
   return (
     <ListStack>
       <li>
@@ -58,8 +58,8 @@ const Template: StoryFn = () => {
           <Textarea
             name="max_length_with_value"
             maxLetters={140}
-            value={value}
-            onChange={onChangeValue}
+            value={value1}
+            onChange={(e) => setValue1(e.target.value)}
           />
         </FormControl>
       </li>
@@ -68,8 +68,8 @@ const Template: StoryFn = () => {
           <Textarea
             name="max_length_with_value_over"
             maxLetters={4}
-            value={value}
-            onChange={onChangeValue}
+            value={value2}
+            onChange={(e) => setValue2(e.target.value)}
           />
         </FormControl>
       </li>
@@ -78,8 +78,8 @@ const Template: StoryFn = () => {
           <Textarea
             name="max_length_with_value_and_decorators"
             maxLetters={140}
-            value={value}
-            onChange={onChangeValue}
+            value={value3}
+            onChange={(e) => setValue3(e.target.value)}
             decorators={{
               beforeMaxLettersCount: (txt) => `entry limit(${txt})`,
               afterMaxLettersCount: (txt) => ` characters(${txt})`,
diff --git a/packages/smarthr-ui/src/components/Textarea/Textarea.tsx b/packages/smarthr-ui/src/components/Textarea/Textarea.tsx
index 54062f2216..e6b5f06025 100644
--- a/packages/smarthr-ui/src/components/Textarea/Textarea.tsx
+++ b/packages/smarthr-ui/src/components/Textarea/Textarea.tsx
@@ -1,6 +1,7 @@
 import React, {
   ComponentPropsWithRef,
   forwardRef,
+  startTransition,
   useCallback,
   useEffect,
   useImperativeHandle,
@@ -12,6 +13,7 @@ import { tv } from 'tailwind-variants'
 
 import { useId } from '../../hooks/useId'
 import { useTheme } from '../../hooks/useTailwindTheme'
+import { debounce } from '../../libs/debounce'
 import { defaultHtmlFontSize } from '../../themes/createFontSize'
 
 import type { DecoratorsType } from '../../types'
@@ -99,6 +101,7 @@ export const Textarea = forwardRef<HTMLTextAreaElement, Props & ElementProps>(
       onInput,
       decorators,
       error,
+      onChange,
       ...props
     },
     ref,
@@ -135,15 +138,24 @@ export const Textarea = forwardRef<HTMLTextAreaElement, Props & ElementProps>(
       }
     }, [autoFocus])
 
-    const onKeyUp = useMemo(
-      () =>
-        maxLetters
-          ? (event: React.KeyboardEvent<HTMLTextAreaElement>) => {
-              setCount(getStringLength(event.currentTarget.value))
-            }
-          : undefined,
-      [maxLetters],
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    const debouncedUpdateCount = useCallback(
+      debounce((value) => {
+        startTransition(() => {
+          setCount(getStringLength(value))
+        })
+      }, 200),
+      [],
     )
+
+    const handleChange = useCallback(
+      (event: React.ChangeEvent<HTMLTextAreaElement>) => {
+        onChange && onChange(event)
+        maxLetters && debouncedUpdateCount(event.currentTarget.value)
+      },
+      [debouncedUpdateCount, maxLetters, onChange],
+    )
+
     const handleInput = useCallback(
       (e: React.ChangeEvent<HTMLTextAreaElement>) => {
         if (!autoResize) {
@@ -189,7 +201,7 @@ export const Textarea = forwardRef<HTMLTextAreaElement, Props & ElementProps>(
         {...textareaStyleProps}
         data-smarthr-ui-input="true"
         aria-describedby={actualMaxLettersId}
-        onKeyUp={onKeyUp}
+        onChange={handleChange}
         ref={textareaRef}
         aria-invalid={error || undefined}
         rows={interimRows}
diff --git a/packages/smarthr-ui/src/libs/debounce.ts b/packages/smarthr-ui/src/libs/debounce.ts
new file mode 100644
index 0000000000..54ce2a552c
--- /dev/null
+++ b/packages/smarthr-ui/src/libs/debounce.ts
@@ -0,0 +1,26 @@
+/**
+ * 関数の呼び出しを指定された待機時間 (wait) だけ遅延させるデバウンス関数。
+ * 直前に同じ関数が呼び出された場合、タイマーをリセットして再び遅延させます。
+ *
+ * @param {T} func - 実行する関数
+ * @param {number} wait - デバウンスの待機時間（ミリ秒）
+ * @returns {(...args: Parameters<T>) => void} デバウンスされた関数
+ *
+ * @example
+ * const debouncedFunction = debounce(() => console.log('Called!'), 200);
+ */
+export const debounce = <T extends (...args: any[]) => void>(
+  func: T,
+  wait: number,
+): ((...args: Parameters<T>) => void) => {
+  let timeoutId: ReturnType<typeof setTimeout> | null = null
+
+  return function (...args: Parameters<T>) {
+    if (timeoutId !== null) {
+      clearTimeout(timeoutId)
+    }
+    timeoutId = setTimeout(() => {
+      func(...args)
+    }, wait)
+  }
+}