To make it possible to enhance the light condensing efficiency of lens parts and to exactly align a substrate.

This process for producing the optical substrate consists in first applying a protective film 2 on base plate glass 1 are executing photolithography for removing the protective film 2 corresponding to the positions where at least the lens parts R of the base plate glass 1 are formed. The base plate glass 1 is chipped with the protective film 2 as a mask to form the prescribed recessed parts R' in the position to be formed with the lens parts 2 and to form recessed parts to be formed as alignment marks. A low-melting glass base 3 is applied on the base plate glass 1 so as to fill the recessed parts R'. This low-melting glass base 3 is fired to be vitrified.