diff --git a/spec/app/pages/timer-page.spec.ts b/spec/app/pages/timer-page.spec.ts
index 551ae61..2c34e1e 100644
--- a/spec/app/pages/timer-page.spec.ts
+++ b/spec/app/pages/timer-page.spec.ts
@@ -14,4 +14,20 @@ jest.mock('@/app/time-up-audio')
 
 describe('TimerPage', () => {
   testMountComponent(() => factory({ shallow: false }))
+
+  describe('computed', () => {
+    describe('scaleStyle', () => {
+      it('style用のオブジェクトを返すこと', () => {
+        const wrapper = factory()
+        wrapper.vm.scale = 1
+        expect(wrapper.vm.scaleStyle).toEqual({ transform: 'scale(1)' })
+
+        wrapper.vm.scale = 0.5
+        expect(wrapper.vm.scaleStyle).toEqual({ transform: 'scale(0.5)' })
+
+        wrapper.vm.scale = 2
+        expect(wrapper.vm.scaleStyle).toEqual({ transform: 'scale(2)' })
+      })
+    })
+  })
 })
diff --git a/src/app/pages/timer-page.vue b/src/app/pages/timer-page.vue
index 1fba5c7..00ccfc5 100644
--- a/src/app/pages/timer-page.vue
+++ b/src/app/pages/timer-page.vue
@@ -8,7 +8,7 @@
     <timer
       time-up-audio-src="timer-timeup.mp3"
       class="timer-wrapper"
-      :style="scaleClass"
+      :style="scaleStyle"
     ></timer>
   </div>
 </template>
@@ -37,7 +37,7 @@ export default class TimerPage extends Vue {
     this.scale = 1
   }
 
-  get scaleClass(): object {
+  get scaleStyle(): object {
     return { transform: `scale(${this.scale})` }
   }
 }