An ultrasonic actuator includes an actuator body configured by alternately stacking piezoelectric layers, and a positive and a negative electrode layers. The positive electrode layer includes a first through a fourth positive split electrodes and a positive diagonal-connection electrode connecting together the first and the third positive split electrodes. The second and the fourth positive split electrodes are connected together outside the positive electrode layer. The negative electrode layer includes a first through a fourth negative split electrodes and a negative diagonal-connection electrode connecting together the first and the third negative split electrodes. The second and the fourth negative split electrodes are connected together outside the negative electrode layer.