To provide a method of manufacturing a motor capable of securing a high coaxiality without strict tolerance management.

Insertion holes 41 penetrating through a gear housing 18 in a shaft line direction of a worm shaft 17 are formed to the gear housing 18, and operation holes 42 facing the insertion holes 41 provided on the gear housing 18 side in an assembled state and having a diameter smaller than that of the insertion holes 41 are formed to a brush holder 13. In a state that the brush holder 13, a yoke housing 4 and the gear housing 18 are temporarily assembled, jig pins 43 inserted into the operation holes 42 via the insertion holes 41 are operated while rotating an armature, that is, while rotating a rotation shaft 6 and the worm shaft 17, to move the brush holder 13. Thereby, an optimum actual assembling position is determined.