In an optical disc in which an information signal is recorded/reproduced by irradiating a laser beam to a disc substrate 1 in which an information signal portion 1c has been provided on one principal plane from the side where the information signal portion 1c exists, a clamp reference surface 3a is set to the information signal portion 1c side of a replica substrate 1a constructing the optical disc. The clamp reference surface 3a is set to a flat surface and a thickness of the replica substrate 1a in a clamping area 3 is set to be larger than that of the convex-shaped replica substrate 1a in an information recording area 4. The replica substrate 1a in which a periphery of a center hole 1b is thicker than the information recording area 4 is used.