In an optical disc, an information signal area on which an information signal can be recorded and/or reproduced is formed on a major surface of a disc substrate thereof; a light transmitting layer which can transmit a laser beam used in a process for recording and/or reproducing the information signal is formed on a side on which the information signal area is present; and a clamp reference plane is arranged on a major surface of the light transmitting layer in a clamp region. If the optical disc is clamped by a chucking unit of a drive, it is clamped by making the clamp reference plane on the major surface of the light transmitting layer contact with a mounting surface of a table for mounting the disc, and making a magnetic metal plate contact with the major surface of the disc substrate, and then sandwiching the optical disc between.