A cylindrical yoke 8 bonded to an inner surface 44 of a cylindrical portion 43 of a rotor case 40 of a motor has a yoke separating slit 85 for separating the yoke 8 in the circumferential direction. A cylindrical rotor magnet 9 is partially bonded to an inner surface 81 of the yoke 8 at a plurality of bonded portions 10 formed apart from one another for the same intervals in the circumferential direction. When the cylindrical portion 43 has been expanded by heat, the yoke separating slit 85 is expanded and the yoke 8 follows the non-bonded portion of the cylindrical portion 43. Therefore, distortion of the cylindrical portion 43 can be prevented. In the non-bonded portions 11 between the yoke 8 and the rotor magnet 9, deformation occurs such that an inner surface 81 of the yoke 8 is separated from an outer surface 92 of the rotor magnet 9. Thus, damage of the rotor magnet 9 can be prevented.