Prior to the start of transfer of an insulation film to a substrate, the degree of opening of a butterfly valve is set small so that evaporation of a solvent component contained in the insulation film is suppressed and the fluidity of the insulation film is ensured at the start of the transfer. On the other hand, the butterfly valve is totally opened at the start of the transfer, so that the pressure inside a thin film forming chamber rapidly decreases and transfer of the insulation film to the substrate is performed always in a low-pressure state (high-degree of vacuum).