PURPOSE: To stabilize the rotation of a rotor by providing a ring rotor with many through holes to insert rotating members such as balls into said holes and by providing a stator with a ring groove to guide said rotating members.

CONSTITUTION: To constitute an ultrasonic motor, a plurality of piezoelectric elements 2 are arranged on one side face of a ring stator 1 and a ring rotor 3 is lap-arranged on the opposite side of said stator 1. Said rotor 3 is provided with many through holes 3a at suitable spaces, rotating members 4 made of metal, etc., are respectively fitted into said holes, and an output terminal 5 is also provided at said rotor 3. Said stator 1 is provided with a ring groove for guiding said rotating members and fitted to a cylindrical member 6 together with the rotor 3. Further, said stator is provided with a ring output member 8 made of metal, which is provided with a ring groove 8a for guiding the movement of said rotating members 4.