A film forming method is provided with a substrate placing step wherein a substrate is placed in a process chamber in an airtight status; a first film forming step wherein the process chamber is supplied with water vapor and a material gas including an organic compound of copper, and an adhered layer of copper is formed on the substrate; an exhaust step wherein the water vapor and the material gas in the process chamber are exhausted; and a second film forming step wherein the process chamber is resupplied with only the material gas and a copper film is further formed on the adhered layer.