PURPOSE: To improve wear resistant performance by forming the side of a rotor which rotates in pressure contact with the surface of a stator which generates a surface wave of graphite-filled polyamide resin to be secured to a rotor ring.

CONSTITUTION: A stator 4 is secured to the outer periphery of a bearing 6 provided in the bottom of a case 7, and a shaft 1 engaged with a rotor 2 is rotatably inserted to the inner periphery. The top of the shaft 1 is rotatably supported by the bearing 9 of a cover 8, and the bearing 9 pressure contacts the rotor 2 with the stator 4. A slider 2a is secured to the rotor ring 2b of the rotor 2 which slides along the traveling wave generating surface 4c of the stator 4. The slider 2a is formed of graphite-filled polyamide resin. Thus, wear resistance can be improved to increase the pressing force of the rotor 2, thereby increasing the output of a motor.