A touch panel has a display region for an operation screen and senses an outer object touching the display region. A vibrator unit applies vibration to the display region. In response to the touch panel sensing the object, a response controller unit instructs the vibrator unit to apply to the display region vibration responsive to the object. The response controller unit checks whether an image processing unit is under waiting or operating condition at the time the touch panel senses the object, and when the image processing unit is under the operating condition, sets the responsive vibration to a level lower than when the image processing unit is under the waiting condition.