PURPOSE: To miniaturize a rotor inserted into a stator and improve performance thereof by unifying a ring-shaped magnet, to which two poles are magnetized in the thickness direction, and a magnetic pole piece, both surfaces thereof have pole teeth oppositely faced to magnetic pole teeth for the stator.

CONSTITUTION: A rotor 26 is inserted into a stator in which a toroidal coil 16 is interposed between two internal stator yokes 12 in the axial direction and an external stator yoke 14. The rotor 26 is constituted by fixing a ring- shaped magnet 28, to which two poles are magnetized in the axial direction, and a magnetic pole piece 32, on both sides thereof magnetic pole teeth 30 oppositely faced to magnetic pole teeth 10 for the stator are formed, to a shaft 34. Accordingly, a rare earth magnet can be used as the ring-shaped magnet 28, a shape is simplified, a motor is miniaturized, and the magnetic pole teeth are fined, thus allowing a change into multi-steps.