A method of forming a nitride film in a fine recess formed in a surface of a substrate to be processed, by repeating a process, which includes adsorbing a film forming raw material gas onto the substrate and nitriding the adsorbed film forming raw material gas. The nitriding the adsorbed film forming raw material gas includes converting a NH3 gas as a nitriding gas, and an adsorption inhibiting gas for inhibiting adsorption of the NH3 gas into radicals and supplying the radicals onto the substrate.