Abstract: In addition to improvement of operability, a small size with a light weight and a long life are achieved. A switch housing unit and a control-part housing unit are provided in a housing, a switch unit provided with a pressure switch which generates an electric signal by performing a pressing operation by a worker is housed in the switch housing unit, a switch cover which covers the pressure switch and which is elastically deformed by the pressing operation by the worker is provided, and the control-part houses a control circuit board which controls a rotation state of a motor in accordance with a magnitude of the electric signal outputted from the pressure switch.