Abstract: A deposited film-forming apparatus by means of high frequency plasma CVD and having a power application electrode arranged in a film-forming vacuum vessel, a high frequency power source connected to said power application electrode, a direct current power source which is connected to said power application electrode and is connected with said high frequency power source in parallel connection, a detector for detecting a symptom of occurrence of arc discharge, and an arc discharge preventive means for preventing occurrence of arc discharge based on said symptom of occurrence of arc discharge which is detected by said detector, wherein said arc discharge preventive means is connected between said power application electrode and said direct current power source such that said arc discharge preventive means is connected with said direct current power source in series connection and is connected with said high frequency power source in parallel connection.