An ultrasonic actuator includes an actuator body, a case and a support rubber. The support rubber is made of conductive rubber having alternately stacked insulating layers and conductive layers and arranged between the case and the actuator body such that an external electrode and an electrode is brought into conduction and applies in advance a compressive force in the direction of longitudinal vibration to the actuator body at a non-node part of the vibration of the actuator body. The support rubber is arranged such that the stacking direction of the conductive rubber intersects with a plane including the direction of longitudinal vibration and the direction of bending vibration of the actuator body.