PURPOSE: To provide a sputtering apparatus constituted so as to be capable of forming a constant film always in high preciseness, by providing a means wherein the intensity of light in a specific wavelength region emitted by glow discharge is measured and a film thickness and a coating speed are controlled by the signal obained through the measurement.

CONSTITUTION: The part of light emitted from a discharge generating region 49 between the target 7 and the substrate 9 in a vacuum container 1 is applied to a plasma spectroscopic monitor apparatus 15 and the intesity of a light with a specific wavelength is subjected to spectroscopic measurement to output signals 16, 17. At the same time, the ratio of the signals 16, 17 is operated to obtain a signal 18. A film forming speed detecting signal 20 is selected from these signals 16, 17, 18 to be inputted to a control circuit 21 and the control signal 22 therefrom is supplied to a sputter power source 8 or a gas introducing system to control a film forming speed to a predetermined value. In addition, the film forming speed detecting signal 20 is inputted to a film thickness detecting circuit 23 and integral operation is carried out to obtain an integral signal 24. The point of time when this signal 24 is coincided with a predetermined value is detected by a film forming final point control circuit 50 and a signal 51 is supplied to a shutter operating mechanism to control the film thickness.