Plate-shaped projections are provided on a front insulator in such a manner as to project towards a front housing. In addition, projecting pieces are provided on a surface of each projection which confronts an inner circumferential surface of a stator housing. The projecting pieces are provided on each projection in such a manner as to form three rows which are parallel to an inner circumferential direction of the stator housing. Spaces between the respective rows constitute guide paths by which the transition wirings which connect between the coils are disposed on the projection in such a manner as to be spaced apart from each other.