To enhance safety by providing a motor for driving a closing element such as a door, a position detector for detecting the position of the closing element, and a control unit which processes signals of the detector to drive the motor.

When the door main body 3 of an overhead garage door or the like is in a fully closed position, a closing force does not work at all, nor is an electric motor 9 exposed to unnecessary load. If a control unit 10 comprising microcontrollers detects via an incremental converter 8 the position of the door main body 3 that has exceeded an allowable position, the motor 9 is driven so that the closing force is immediately applied to the door main body 3. The closing force used in this operation varies depending on the position of the door main body 3 and as the position varies. Setting the closing force to a maximum value corresponding to the maximum stopping action of the motor 9 from a certain position is most simple, and the motor 9 is actuated simply by being switched on. Thus safety can be enhanced through simple design.