To provide a method of cutting a film mirror reducing decrease in specular reflectance due to deterioration of a silver layer that is a reflective layer, having light weight and flexibility, allowing increase in area and mass production while reducing manufacturing costs, having superior weather resistance, and having good specular reflectance to solar heat, and to provide the film mirror obtained by the same and a reflecting apparatus for solar thermal power generation using the same.

The method of manufacturing the film mirror including a resin substrate, and a silver reflective layer and a protective layer on the resin substrate is characterized in that the temperature of a part of a tool in contact with the film mirror is higher than a glass transition temperature of a resin constituting the resin substrate, in a process of cutting the film mirror.