PURPOSE: To assure the specified ultrasonic output to a cleaning tank by providing the apparatus with an oscillator, an output stage for supplying an ultrasonic output signal and an output control means having pulse-width modulation means arrayed to supply a correction signal to the output stage.

CONSTITUTION: The output stage 16 which receives the supply from a mains power supply and receives the signal from the oscillator 22 supplies the ultrasonic output signal. The output control means 26 has a sensing means 34 for monitoring the output signal from the mains power supply to the output stage 16 or the output stage 16 and the pulse-width modulation means 24 which are connected to the sensing means 34 and arrayed to supply the correction signal to the output stage 16 so as to maintain the mains power supply currents or ultrasonic outputs in a pair constant with respect to the specified main power source voltage. Consequently, the specified ultrasonic output from generators 10a to 10c to the cleaning tank 12 may be assured.