PURPOSE: To maintain a film forming speed at a desired value with a sputtering device using magnetron sputtering by regulating the current to be impressed to a target to an optional value to control the drop of the discharge voltage by the recess of the target.

CONSTITUTION: After the inside of a vacuum vessel 1 is evacuated, a diluting gas such as Ar is introduced therein and electricity is conducted from a power source 15 to an electromagnet 10 formed of a backing plate 6 to support the target 7 and a holder 8; at the same time, a magnetron discharge is effected on the surface of the target 7 by a sputtering power source 13. Ar is ionized by such discharge to sputter the target 7 so that the film of the target material is formed on a counter substrate 5. The surface of the target 7 is recessed by the sputtering in this case, by which the discharge voltage is dropped and the film forming speed is lowered. The discharge voltage is measured by a voltmeter 14 in order to prevent such voltage drop and is compared with a set discharge voltage by a control device 16. The magnetic field intensity of the recessed surface of the target 7 is controlled to be constant by controlling the current of the electromagnet power source 15 according to the difference therebetween and the film forming speed on the substrate is maintained at a desired speed by subjecting the sputtering power source 13 to constant current control.