PURPOSE: To form a thin film having good quality on a base plate by installing the base plate on one of the two electrodes facing each other, maintaining preliminarily the other electrode at an adequate temp., impressing a voltage between both electrodes and executing a plasma CVD method.

CONSTITUTION: Two electrodes consisting of stainless steel are disposed to face each other and a voltage is impressed between both electrodes to form a thin film on a base plate installed to one of the electrodes by a plasma CVD method. The other electrode on which the base plate is not installed is maintained at ≥200°C by using a device provided with means for heating from before the formation of the thin film in the stage of forming the thin film in the above-mentioned way. The peeling of the film from the opposed electrodes is thus decreased and the discharging of the adsorbed moisture is made easy, by which the sticking of flake to the inside of the thin film or the adsorption of oxygen thereto is prevented and the thin film having good quality is formed.