PURPOSE: To prevent an optical disk substrate from curving in a heat treating process as to the manufacture of the optical disk substrate.

CONSTITUTION: A shape memory film 4 which is so memorized as to curve in a shape, canceling the curvature shape of the substrate 1 for optical disk formation caused in a treating process wherein heat is generated, at the temperature of said treating process is stuck on one surface of said substrate 1, thereby absorbing the curvature of the substrate 1 due to stress applied to the substrate 1 in the treating process.