Not less than two regions different in magnetic circuit design are provided in a rotational axis direction of the rotor (30), the regions being different by changing a cross-sectional shape in the rotational axis direction in a cross-section perpendicular to a rotational shaft (10) of the rotor (30) having the permanent magnets (1) and the rotor core (2); the supplemental grooves (5) are provided in axial partial regions of each of the teeth (7) of the stator core (3); and the region in which the supplemental groove (5) is provided is each partial region for each region facing a region same in magnetic circuit design of the rotor (30). This enables to reduce cogging torque generated by variations on the rotor side.