To perform the reproduction of a die at low cost.

A platinum group based metal plating layer 20 is provided on the surface of a base material 15, as a machining layer. The desired optical face shape is finished with high precision by ultraprecisely machining the machining layer using a diamond bit. The surface thereof is provided with a surface protective film layer 21 and a die release layer 22. Regarding the die in which the die release layer 22 and the surface protective film layer 21 are deteriorated by the repetition of heating and cooling by being used for the process of molding, the molding face is immersed into hydrofluoric acid, the deteriorated surface protective film layer 21 and die release layer 22 are removed, and a surface protective film layer 21 and a die release layer 22 are newly attached, so as to reproduce the die. Since the platinum based metal plating layer 20 is not eroded by hydrofluoric acid, the shape of the optical face subjected to the ultraprecise working is maintained.