An ultrasonic actuator (3) includes an actuator body (4) performing a plurality of vibrations including a bending vibration, and a driver element (5) which is attached to a long side surface (40b) of the actuator body (4), and outputs a driving force by making an orbit motion in response to the vibrations of the actuator body (4). The driver element (5) is provided with an attachment surface (51), and is attached to the long side surface (40b) with the attachment surface (51) in surface contact with the long side surface (40b). A width of the attachment surface (51) in the longitudinal direction of the long side surface (40b) is smaller than a maximum width of the driver element (5) in the longitudinal direction of the long side surface (40b).