Ultrasonic motor having a plate-shaped vibrating body

An ultrasonic motor comprising:

• a stator that includes a plate-shaped vibrating body including a first main surface and a second main surface that oppose each other;
• a piezoelectric element on the first main surface of the plate-shaped vibrating body;
• a mass addition portion;
• and
• a rotor in direct or indirect contact with the second main surface of the plate-shaped vibrating body,
• wherein the piezoelectric element is disposed along a circumferential direction of a traveling wave and is configured to vibrate the plate-shaped vibrating body to generate the traveling wave circulating around an axial direction,
• wherein the piezoelectric element is configured to vibrate the plate-shaped vibrating body in a vibration mode including a nodal line that extends in the circumferential direction, and
• wherein the mass addition portion is disposed along the circumferential direction on at least one of the first main surface and the second main surface of the plate-shaped vibrating body, and is located outside the nodal line in a direction perpendicular to the axial direction.