A film forming method includes: accommodating a substrate in a processing container of a film forming apparatus; supplying an inert gas to the processing container at a flow rate equal to an average flow rate of a plurality of gases to be supplied into the processing container in a film forming process and maintaining a pressure of the processing container to be substantially same as an average pressure of the processing container in the film forming process; and alternately supplying the plurality of gases into the processing container and forming a film on the substrate.