To provide an optical disk which can have data record on its lands and grooves to high density and have data recorded in an address area by using the address area and a data area in common.

The optical disk 3 has information recorded and reproduced on a track Tr composed of a groove 1 and a land 2. The track Tr has zigzag parts 1A1 and 2A1 and nonzigzag parts 1A2 and 2A2 formed alternately, and the parts 1A1 and 2A1 have a 1st zigzag 1a formed on one side 1A1b of the track Tr and a 2nd zigzag 1b formed on the other side 1A1a of the track Tr; and the start positions (c) of the zigzags 1a and 1b are in a same phase with each other on the track and the zigzags 1a and 1b are aligned with the same radial line 1A11 at least once in every rotation of the disk.