A gas supply mechanism of supplying a raw material gas obtained from a raw material of a solid state or a liquid state into a chamber configured to perform a film forming process on a workpiece is disclosed. The gas supply mechanism includes a gas supply controller configured to control a flow rate of a carrier gas by means of a flow rate controller, and to enable the carrier gas to flow while closing a material gas supply/shut-off valve to thereby increase internal pressures of a raw material container and a raw material gas supply pipe to be a high-pressure condition and then control the raw material gas supply/shut-off valve to be opened.