The yoke 22 includes; an annular yoke cylindrical portion (cylindrical portion) 22a centered on the rotation axis J; and a plurality of yoke protruding portions (protruding portions) 22b protruding to the inner side in the radial direction from an inner circumferential surface of the yoke cylindrical portion 22a. The yoke cylindrical portion 22a is arranged on the outer side of the stator 30 in the radial direction. The plurality of yoke protruding portions 22b are arranged at substantially equal intervals in the circumferential direction.

The magnet 23 has a rectangular plate shape that is long in the axial direction. In the present example embodiment, a plurality of magnets 23 are provided. In the present example embodiment, forty-two magnets 23 are provided. The magnet 23 is fixed to an inner circumferential surface of the yoke 22 using, for example, an adhesive or the like. More specifically, the plurality of magnets 23 are fixed to a part sandwiched between two yoke protruding portions 22b adjacent in the circumferential direction on a surface facing the inner side of the yoke cylindrical portion 22a in the radial direction. The magnet 23 has an N magnetic pole or an S magnetic pole on an inner circumferential surface. The magnet 23 having the N magnetic pole and the magnet 23 having the S magnetic pole are alternately arranged along the circumferential direction.