To prevent the generation of uneven rainbows at the time of curing an active ray curing substance layer by irradiating the layer with active rays in the case of continuously forming an active ray cured layer on a resin film and to provide an optical thin film such as an antireflection layer having no uneven application when the optical thin film is formed on the active ray cured layer by application.

In the optical film manufacturing device, the active ray curing substance layer is applied to a carried resin film and a shielding plate is arranged on a position where the surface of a free span is not directly irradiated with active rays in the case of curing the resin film by irradiating it with active rays by using a plurality of active ray light sources while supporting the rear surface of the resin film by a backup roll.