The object of the present invention is to provide an apparatus and method for forming a deposited film which can repeatedly form a large amount of functional deposited films with good reproducibility without degradation in the characteristics of films formed even when gas leakage occurs in a shut-off valve, and without reducing the yield as a result when gas leakage occurs in the shut-off valve, by immediately detecting and repairing it. The deposited film forming apparatus according to the present invention comprises: a chamber capable of maintaining an interior thereof under vacuum; a source gas supply piping for supplying a source gas into the chamber; an evacuation system piping for evacuating the interior of the chamber; a gas supply piping for use in opening to atmosphere, for supplying a gas for returning a pressure within the chamber to atmospheric pressure, wherein a plurality of shut-off valves are provided in series between a gas source of the gas for returning the pressure within the chamber to the atmospheric pressure and the chamber, and a pressure-gauge and/or evacuating means are provided between the plurality of shut-off valves.
