In a film-forming process with a capacitively-coupled plasma (CCP) chemical vapor deposition (CVD) device, pulse control is performed on a low-frequency radio-frequency power source. During the pulse control, an ON time and an OFF time form one period. Furthermore, in the pulse control, a time interval between a time period from the moment that the electric power supply is stopped till the electron density decreases to a residual plasma threshold capable of causing an arc discharge and a time period from the moment that the electric power supply is stopped till the density of high-temperature electrons decreases to a specific plasma state serves as the OFF time; a saturation time during the rising process of the density of the high-temperature electrons in the plasma after the electric power supply is started serves as an upper limit of the ON time; and electric power is intermittently supplied under the above conditions.