A metal gear cover 43, which is provided so as to cover a worm wheel housing 36b, is disposed between a worm wheel 41d and a circuit board 51 and grounded, thereby quickly introducing exogenous noise “ON” such as static electricity to the outside of the sunroof motor 21, even if exogenous noise “ON” enters the sunroof motor 21 and reaches the gear cover 43. Therefore, it is possible to surely prevent exogenous noise “ON” from being reflected to the circuit board 51, and causing the circuit board 51 to malfunction and the like. Furthermore, it is possible to improve reliability of the sunroof motor 21.