PURPOSE: To enable to attain a high plasma density and a comparatively low particle energy discharge at a low cathode voltage by arranging electromagnets around a target.

CONSTITUTION: The target 7 is arranged in a vacuum chamber 1. A cathode tab (electrode) connected with a power source 6 is connected with the target 7. Magnet devices 14, 15, 16 make the magnetic field go out of the target 7 and enter therein again. Microwave is guided into a region of the target 7. Further, electromagnets 40, 41 are arranged around the target 7. The microwave is supplied into two cavity resonators 25, 26 arranged by being apart from each other with some distance and is guided in a region before the target 7 from the resonators 25, 26. Thereby pressure at the point of starting discharge can be reduced.