On an optical disk medium according to the present invention, address information is recorded along a wobbling track groove 2. The track groove 2 is made up of a plurality of unit sections 22, 23. Each of these unit sections 22, 23 has side faces that are displaced periodically in a disk radial direction. This displacement oscillates at a single period in a tracking direction. However, the displacement pattern differs depending on nulleach bit of address information (subdivided information)null allocated to each of the unit sections 22, 23.