PURPOSE: To apply the oscillator to an ultrasonic wave generator by providing an oscillation circuit, a frequency divider circuit and a control circuit to the oscillator so as to output the part of its oscillating signal.

CONSTITUTION: An oscillation circuit 100 outputs continuously an oscillating frequency signal from a crystal vibrator 101 as a signal A. Then the signal A is fed to a FF 201 of a frequency divider circuit 200 and a TG 305 of a control circuit 300. A Q output signal of the FF 201 implementing frequency division is given to a input of a DFF 302 of a control circuit 300, an inverted Q output signal of the FF 201 is given to a input of a DFF 303 of the control circuit 300 as a frequency division signal C. When an input signal D given to an external input terminal 401 of an oscillator 10 is changed, one pulse of a crystal oscillation signal A passes through a TG305 and one pulse is led to an output terminal 402 via a capacitor 306.