PURPOSE: To prevent short circuit fault between terminals in a ultrasonic actuator easily with low cost by providing a dust-proof function of rubber and the like in the gap between vibrators.

CONSTITUTION: A ultrasonic actuator 1 is constructed such that a longitudinal vibrator 2 and a flexing or torsional vibrator 3 are fixed to a plate 4 which is attracted to a base 11 through a pressure contacting means comprising a magnet 5 and a rigid iron board 6 is adhered thereto. A dust-proof means 50 comprising a silicon rubber is placed in the gap between the vibrators 2, 3 in order to prevent abrasion powder produced from the actuator or dust intruding therein. The vibrators 2, 3 are connected through the terminal block 8 on the plate 4 and an external cable 9 to a power source driver 13 and a controller 14.