An optical disk suppressing the time required for a startup of a recording/playback apparatus from unduly increasing, even when there is (i) one type of disk where information is recorded on a groove track, and (ii) another type of disk where information is recorded on a land track. Both types of optical disks having a control data area, and a data recording area in which user data is recorded. A code for indicating the groove track or the land track onto which tracking servo control is executed is provided in the control data area of both types of optical disks.