To reliably fix a motor housing, an end bell, and a gear box of a reduction gear portion without special change to the design of a method for fixing the end bell to the motor housing.

The end bell made of resin is fitted to an opening of the motor housing and an rotating shaft penetrating the end bell with a bearing housed therein is extended into the reduction gear portion. The reduction gear portion includes the gear box made of resin for housing a worm fixed on the rotating shaft and a helical gear engaged therewith. A stepped portion in the resin gear box is opposed to one side of an end bell flange portion in the direction of the axis of the shaft. Multiple integrally molded projections are provided on the surface of either of the end bell and the gear box opposed to each other. These projections are pressed against the surface of the other of the end bell and the gear box opposed to each other and the gear box is fixed to the motor housing.