PURPOSE: To provide an inexpensive waterproof device for motor in which no waterproof cover is used and accuracy is ensured without cutting the frame.

CONSTITUTION: A bracket is press fit to microprotrusions 11 provided partially at several points in the peripheral direction on the open end of a frame 1 in order to keep airtightness in the peripheral direction. Microrecesses 12 having peripheral width shorter than that of the microprotrusion are provided in the center of the end face of microprotrusion. Accuracy of end face is then set for the remaining part 13 of microrecesses and the end face is abutted on the plane of the bracket thus keeping airtightness in the axial direction. This structure provides a waterproof device for motor without requiring any waterproof cover or cutting.