According to an embodiment of present disclosure, a film formation method is provided. The film formation method includes supplying a first process gas as a source gas for obtaining a reaction product to a substrate while rotating a turntable and revolving the substrate, and supplying a second process gas as a gas for nitriding the first process gas adsorbed to the substrate to the substrate in a position spaced apart along a circumferential direction of the turntable from a position where the first process gas is supplied to the substrate. Further, the film formation method includes providing a separation region along the circumferential direction of the turntable between a first process gas supply position and a second process gas supply position, and irradiating ultraviolet rays on a molecular layer of the reaction product formed on the substrate placed on the turntable to control stresses generated in a thin film.