To provide an ultrasonic motor which includes a piezoelectric vibrator with a side-to-side ratio different from that of a conventional piezoelectric vibrator, has a simple structure, and generates a sufficient thrust force.

The ultrasonic motor generates a driving force by causing the rectangular piezoelectric vibrator 1 to vibrate in a multivibration mode that is a combination of a first vertical vibration mode and a second bending vibration mode. When the length in the direction of expansion/contraction at the vibration of the piezoelectric vibrator 1 in the first vertical vibration mode is L and the length in the direction of shearing at the vibration of the piezoelectric vibrator 1 in the second bending vibration mode is w, the piezoelectric vibrator 1 is formed to determine the value of w/L to be substantially 0.26. Two slide chips 1c are disposed on both longitudinal ends of the piezoelectric vibrator 1. The piezoelectric vibrator 1 includes four electrodes 4a and 4b on its main surface 1b, and an AC power supply 5a which applies an AC voltage to the electrodes 4a to drive the piezoelectric vibrator 1.