PURPOSE: To reduce a noise current by connecting electrically an electrostatic shielding member enclosing an ultrasonic vibrator to the shield wire of a connecting cable.

CONSTITUTION: An electrostatic shielding conductor 61 made of a gold net or a thin metallic plate so as to cover the oscillator 51 is provided at a protection case W, and an insulating molding agent 62 is filled in the case W. Then, the conductor 61 is connected to the shield wire of a balanced 2-core cable 53. Thereby, since impedance at both terminals of the cable 53 is low, a current that flows to the oscillator 51 due to an induced voltage is reduced, and the noise current can be reduced without being limited by the stray capacitance of the transistor used.