To provide a process for producing an optical substrate capable of preventing the incidence of unnecessary light.

A high-refractive index transparent adhesive 4 is applied on a glass substrate and after a stamper S is pressed thereto from above, this adhesive is temporally cured. The stamper S is thereafter removed and the high-refractive index transparent adhesive 4 is normally cured to form a microlens array part MR. A black mask is formed on at least its periphery. Cover glass is stuck to the high-refractive index transparent adhesive 4 via other translucent adhesive having the refractive index different from the refractive index of the high-refractive index transparent adhesive 4 constituted with at least the microlens array part MR. The cover glass or substrate glass is formed to a prescribed thickness.