PURPOSE: To stably keep a magnetron discharge in a magnetic-field which changes its direction and strength, and perform the magnetron discharge which will not be influenced by magnetic-field variation of discharge current.

CONSTITUTION: The anode 1 is thin and circular. The distance from its symmetical axis, i.e. the length in which its radius is minimized is some 0.5.mm. The cathode plate section 12 is located, inserting the anode 1. DC high voltage is applied between the electrode plate sections 12 and the anode 1 from the DC high voltage power supply 4. The central cathode is located at the center of the anode 1 in the same way as the central cathode 2a. The central electrode 11 is electrically insulated from the cathode plate sections 12. Negative voltage is applied to the cathode plate sections 12 from the DC power supply 9.