PURPOSE: To perform a stabilized magnetron discharging in vacuum by cooling a magnetic field generation system and a cathode.

CONSTITUTION: A through hole 1a of a flange 1 for the extra high vacuum use fitted air tightly to a flange 2 installed on a wall surface of a vacuum container is connected with the inner part of a central part cathode 6a of a cathode 6 by means of Kovar rings 16, 18, an alumina ceramic insulating pipe 17, a nonmagnetic stainless steel piping 19, and a flange 20, and together with this, a through hole 1b is connected with an annular air tight container 4 inner part by means of a piping 34 and flanges 32, 33, 35. And further, the central part cathode 6a inner part is connected to the annular air tight container 4 inner part by means of Kovar rings 21, 23, an alumina ceramic insulating pipe 22, a nonmagnetic stainless steel pipe 24, flanges 25, 26, 30, 31 and a cooling water piping 27. With this, the cathode 6 and the magnetic field generation system 3 are cooled, thus enabling magnetron discharging in vacuum without generating excessive heat damages.