A motor rotates a cam, thereby pulling up an external force application member while compressing an application spring. After that, the motor releases the external force application member to impact a sheet material. An impact force caused at a time when an external force receiving member receives an external force application member through the sheet material is detected by a piezoelectric element. When an electric power supply to the motor is stopped, a retraction spring allows the motor to idle through a wheel and rotates the cam to allow the external force application member to retract to a highest position.