The present claimed invention is a film forming system 1 that forms a film by vaporizing a liquid precursor and then depositing the vaporized liquid precursor on a substrate 2, and comprises a chamber 3 inside of which the substrate 2 is held, an injection valve 4 that directly injects the liquid precursor into the chamber 3, and a control unit 11 that alternately sets a supplying period while the liquid precursor is directly injected into the chamber 3 to supply the liquid precursor in a vaporized state and a supply halt period while the liquid precursor is not supplied into the chamber 3 and controls the supplying period and the supply halt period by periodically opening and closing the injection valve 4 so as to intermittently supply the liquid precursor into the chamber 3, and is characterized by that the control unit 11 controls the supply halt period to be equal to or longer than a migration/evaporation period necessary for atoms or molecules of the liquid precursor deposited on the substrate 2 to migrate and necessary for a reaction by-product material generated on the substrate 2 to evaporate. An object of this invention is to generate a thin film of high grade having less impure substances.