To provide an optical disk having a physical format system which is appropriate to handle data of a large capacity such as image and audio data or the like and can easily secure compatibility to a read-only type optical disk.

An optical disk 1 is a reload type optical disk such as a phase change medium, an MO(magneto-optic) medium or the like, or a write-once type optical disk such as a pigment-based medium or the like. A physical format of these disks is constituted so that a track 2 is divided to a plurality of zones 21-2n in a radial direction of the optical disk 1. The tracks 2 for recording data are formed to serpentine wobbling with an optional constant cycle set different for each divided zone in the radial direction of the optical disk 1.