An insulating bobbin to be mounted on a stator core has a tooth-endface facing portion that faces an endface portion, in an axial direction, of the tooth portion and a tooth-side-surface facing portion that faces a tooth side surface portion, in a circumferential direction, of the tooth portion; the tooth-side-surface facing portion has a first abutting area that abuts on the tooth side surface portion, a second abutting area that abuts on the tooth side surface portion at a more outer side in a radial direction than the first abutting area abuts thereon, and a middle inner wall surface portion that is situated between the first abutting area and the second abutting area and faces the tooth side surface portion via a space.