PURPOSE: To improve the processing effect by the vibration electric field by extending a branch line into a circuit from input terminals to the front stage of a high-frequency generating section, connecting a light receiving section to the branch line, providing a light source for the light receiving section, and installing the light receiving section in the magnetic field.

CONSTITUTION: The AC voltage from input terminals 11, 12 is fed to a high-fre quency generating section 20 via a power source section 10 together with the electrical signal from a light receiving section 60 and converted into high-fre quency voltage. This voltage is boosted by a booster section 30 into high-fre quency high voltage, and the DC component is removed by the output capacitor 43 of a converting section 40. The vibration electric field is formed in a processing chamber by the high-frequency high voltage, and an object to be processed is processed by its action.