PURPOSE: To provide higher efficiency with a device that forms a functional film in a vacuum, by providing means for intermittent or continuous replacement of internal members, under vacuum, or a means far purification.

CONSTITUTION: Valves 106 and 107 are opened for the gas to be introduced from a gas supply facility 116, and while exhausting with a pump 108, a power is introduced from a power source 109 for discharge, so that a film of a specified thickness is deposited on a base body 104. While a motor 103 intermittently rotating a sticking prevention member 101, valves 113 and 114 are opened, so that a gas supply facility 117 introduces etching gas and a pump 115 exhausts. The pressure in the purification space is set lower that in film-forming space, and a discharge electrode 111 is applied with power by a high frequency power source 112, so that the film deposited an the sticking prevention member 101 is removed. With this method, longer film-farming period is attained, for improved yield and stable film quality.