Abstract: A technique that includes: a substrate holder provided with a substrate mounting table on which a substrate is mounted; a substrate transferrer configured to load or unload the substrate onto or from the substrate mounting table; a process container configured to accommodate the substrate holder holding the substrate; a film-forming gas supply system configured to supply a film-forming gas to the substrate in the process container; and a controller configured to be capable of controlling the substrate transferrer and the film-forming gas supply system to interrupt execution of a film forming process for supplying the film-forming gas to the substrate and perform a process for separating the substrate mounted on the substrate mounting table at least once until a film having a desired thickness is formed on the substrate after the film forming process is started.