PURPOSE: To easily reduce in size of an actuator by employing an ultrasonic vibrator as driving means for applying driving force of two degrees of rotary freedoms to a movable element.
CONSTITUTION: A 2-degree-of rotary freedoms actuator 1 has ultrasonic vibrators 2a, 2b and a semispherical movable element 3. The vibrators 2a, 2b are attached with a first piezoelectric unit 22 for exciting a bending vibration at an elastic unit 21 on the upper surface of the unit 21 having a rectangular flat plate shape. A second piezoelectric unit 23 for exciting a vertical vibration is attached to the side face substantially perpendicular to the attaching surface. As a result, when an electric signal of a predetermined frequency is applied to the first, second units 22, 23, the predetermined position of the unit 21 is excited substan tially by an elliptical vibration, and a driving force in the direction of an arrow A is applied to a contact surface 31.