PURPOSE: To surely resiliently support a bearing by a wave-shaped washer by eliminating its biting, deformation, breaking, bending, etc., at the time of press-fitting a housing, in the case of an assembly process of a motor.

CONSTITUTION: Compressed air is fed into a bearing holding part 5a from a compressed air blow port 7a of a press-fit jig 7, brought into press contact with the back surface of a housing 5, to float a wave-shaped washer 6, and by press-fitting the housing 5 to a stator 1 in a condition that the wave-shaped washer 6 is inscribed to the back surface of the bearing holding part 5a, the wave-shaped washer 6 is normally pinched between a bearing 4a and the housing 5 to surely elastically support the bearing 4a, so that noise generation and torque insufficiency of a motor can be eliminated.