An optical disk is constructed such that a thin film including a reflective layer is formed on a substrate, or on a thermoplastic resin layer on the substrate. A stamper having an asperity pattern corresponding to information signals is directly pressed against the thin film to transfer the asperity pattern on the thin film. Heat-pressing the stamper against the thin film makes it possible to further accurately transfer the asperity of the stamper to the reflective layer with less pressing force in the case where the reflective layer is formed on a thermoplastic resin layer.