PURPOSE: To control the concn. of reactive gas on the central part and circumferential part of plasma at the time of introducing Ar and reactive gas in reactive sputtering.

CONSTITUTION: In the process of sputtering, reactive gas is introduced through gas piping 3, and Ar or reactive gas is independently introduced from a ring- shaped gas piping 4, by which the concn. control of the reactive gas in the diameter direction of a target 2 is executed to uniformize the reaction between the reactive gas and the target 2 in the face of the target.