A rigid optical sheet manufacturing method capable of manufacturing an optical sheet at high productivity and low manufacturing costs, and an optical sheet are provided. An optical sheet 1 includes a transparent thermoplastic resin base 2 formed of a thermoplastic resin that is rigid at temperatures not higher than its glass transition point, and a first optical structure 3 formed on one of the surfaces of the thermoplastic resin base 2. The first optical structure 3 is formed by pressing a material for forming the first optical structure 3 together with the flexible thermoplastic resin base 2 having a surface temperature not higher than the glass transition point and an internal temperature not lower than the glass transition point by a radiation-curable resin shaping roller 14. Preferably, the material forming the first optical structure 3 is a radiation-curable resin. Preferably, a film 6 having high adhesion to both the thermoplastic resin and the radiation-curable resin is formed on one of the surfaces, on which the first optical structure 3 is to be formed, of the flexible thermoplastic resin base 2. Preferably, a second optical structure 4 is formed on the other surface, opposed to the surface on which the first optical structure 3 is formed, of the flexible thermoplastic resin base 2.