TWI764904B

By simultaneously conducting electricity to a plurality of sputtering chambers during preliminary film formation when producing an optical film for forming a multilayer optical thin-film on a film substrate, the present invention forms a layered thin-film body of two or more different material types on a film substrate, and calculates the film thickness of the plurality of thin-films on the basisof the optical properties obtained by an optical measurement unit (80) provided in the sputtering device. The film thickness measurement and thin-film formation conditions are repeatedly adjusted until the optical properties obtained by the optical measurement unit or the film thickness of the plurality of thin-films calculated on the basis of the optical properties falls within a prescribed range.