diff --git a/src/Checkbox/Checkbox.test.tsx b/src/Checkbox/Checkbox.test.tsx
new file mode 100644
index 0000000..4adc3bb
--- /dev/null
+++ b/src/Checkbox/Checkbox.test.tsx
@@ -0,0 +1,29 @@
+import { renderToStaticMarkup } from 'react-dom/server'
+import { describe, expect, it } from 'vitest'
+
+import { Checkbox } from './index'
+
+/** SSR 出力からルートの label の class 属性をクラス名の配列として取り出す */
+const getRootLabelClasses = (html: string): string[] => {
+  const className = html.match(/^<label[^>]*\bclass="([^"]*)"/)?.[1]
+  if (className === undefined) {
+    throw new Error(`ルートの label に class 属性が見つかりません: ${html}`)
+  }
+  return className.split(' ')
+}
+
+describe('Checkbox', () => {
+  it('渡した className がルートの label にマージされる', () => {
+    const html = renderToStaticMarkup(<Checkbox className="my-card">ラベル</Checkbox>)
+    const classes = getRootLabelClasses(html)
+
+    expect(classes).toContain('aria-checkbox')
+    expect(classes).toContain('my-card')
+  })
+
+  it('className を渡さない場合は既存のクラスのみが付く', () => {
+    const html = renderToStaticMarkup(<Checkbox>ラベル</Checkbox>)
+
+    expect(getRootLabelClasses(html)).toEqual(['aria-checkbox'])
+  })
+})
diff --git a/src/Checkbox/index.tsx b/src/Checkbox/index.tsx
index 43fe752..69a4354 100644
--- a/src/Checkbox/index.tsx
+++ b/src/Checkbox/index.tsx
@@ -60,7 +60,7 @@ const useCheckboxState = (ref: React.RefObject<HTMLLabelElement | null>) => {
  *
  * @summary 複数選択用のチェックボックス
  */
-const Checkbox = ({ children, ...props }: CheckboxProps) => {
+const Checkbox = ({ children, className, ...props }: CheckboxProps) => {
   const ariaRef = useRef<HTMLLabelElement>(null)
   const { isSelected, isIndeterminate, isDisabled, isHovered, isFocused } =
     useCheckboxState(ariaRef)
@@ -78,7 +78,7 @@ const Checkbox = ({ children, ...props }: CheckboxProps) => {
   })
 
   return (
-    <AriaCheckbox {...props} ref={ariaRef} className="aria-checkbox">
+    <AriaCheckbox {...props} ref={ariaRef} className={clsx('aria-checkbox', className)}>
       <div className={checkboxClasses} />
       {children && (
         <Typography component="span" className={labelClasses}>