PURPOSE: To provide an optical disk device capable of stabilizing a focus servo system by suppressing a mechanical vibration of the optical disk, even if the optical disk having a different structure is used.

CONSTITUTION: The optical disk 11 in which a hub 14 and a magnetic plate 15 are eccentrically fixed at the center part of the disk substrate 11, is put into a rotary shaft 10 and supported by a rotation supporting part 18 in recessed shape which is penetrated and fixed to the rotary shaft 10. By a permanent magnet plate 19 mounted inside the rotation supporting part 18, an oppositely faced magnetic plate 15 is magnetically attracted to rotate the optical disk. A viscoelastic member 21 is inserted between the bottom of rotation supporting part 18 and the permanent magnet plate 19, then the vibration of optical disk caused by an external force is suppressed by fixing the permanent magnet plate 19 to the bottom.