It comprises stator including stator core having yoke and a plurality of teeth protruded from yoke, which is formed with slots between adjacent teeth, and rotor having rotor core and permanent magnet formed with a plurality of magnetic poles, which confronts tip ends of teeth via gaps, wherein rotor core is formed by rotor core materials circumferentially equally divided into the predetermined number of divisions, and the least common multiple being N for the number of slots and the number of magnetic poles and the least common multiple being M for the number of slots and the number of divisions, then N is equal to M.