PURPOSE: To reduce the size and weight of a device and to improve its maintainability by providing a motor and a worm gear transmitting its rotation driving force to a wiper shaft in a motor case and by constituting the drive shaft of the motor and the worm gear separately.

CONSTITUTION: A motor case 1 is produced by molding a resin, for instance, and a cover 1b is fastened to a case section 1a with bolts 1c in assembling. A motor 8 is inserted and fixed in fixed projections 8b provided inside the case section 1a, and the front tip 9a of a worm gear 9 is rotatably inserted in a projections 9d provided inside the case section 1a and the rear tip 9b is supported by the drive shaft 8a of the motor 8, thus the worm gear 9 is suspended between the projections 9d and the motor 8. Accordingly, the worm gear 9 and the drive shaft 8a of the motor 8 are separably constituted as separate bodies, and for instance, the worm gear 9 with a large diameter and the motor 8 with a small size can be used to attain a desired objective.