A film forming apparatus includes a first supply unit configured to supply a first reaction gas into the reaction vessel under an environment of a first pressure, a second supply unit configured to supply a second reaction gas into the reaction vessel under an environment of a second pressure lower than the first pressure, a first vacuum exhaust mechanism connected to the reaction vessel through a first exhaust path in order to create the environment of the first pressure within the reaction vessel, a second vacuum exhaust mechanism connected to the reaction vessel through a second exhaust path in order to create the environment of the second pressure, the second vacuum exhaust mechanism being lower in an operation pressure zone than the first vacuum exhaust mechanism, and a switching unit configured to switch exhaust destinations of the reaction vessel between the first path and the second path.