An optical disk is operated in a ZCLV system for generating a stable and precise clock and the operation proceeds with a speed change of a high-speed motor when data is stored with the motor accelerated or decelerated at a high speed to improve accessibility for data storage. The optical disk includes: a disk rotator for rotating the optical disk at an optional number of rotations; a rotation controller for controlling rotation of the optical disk; a wobble extractor for extracting wobbling on the track of the optical disk; a clock extractor for extracting a clock element from the wobbling; a speed detector for detecting a linear speed of the optical disk; and a response switch for switching a response of the clock extractor, in which the response of the clock extractor is switched depending on the linear speed of the optical disk.