PURPOSE: To make the efficiency of an apparatus higher by connecting a semiconductor switching element between an inverter and a high-voltage transformer and by changing the excitation frequency of said switching element.

CONSTITUTION: A corona discharge processor is composed of a power supply part 1, a switching element exciter part 2, an inverter part 3, an output part 4, and a corona discharge part 5. Said power supply part 1 is a DC power supply, and a switching element exciter part 2 surely performs the switching operation of a semiconductor switching element 6 of said inverter part 3 to make its period variable. Then, the inverter part 4 switches by said element 6 the conducting angle of DC power from the power supply part 1 according to a signal from the switching element exciter part 2. Thus, a high frequency high voltage is generated in the secondary coil 4 of said high-voltage transformer 10 and a corona discharge, in the corona discharge part 5. Said power can be controlled by changing the period of said exciter part 2.