A clamping device with variable clamping force of an optical disk drive is disclosed. The main structure consists of a base, a resilient body with restoring property, an annulus magnet (or an annulus yoke) which can exert attraction force to a turntable for clamping disk, and a linking member which can change height of the annulus magnet (or the annulus yoke) relative to base according to the centrifugal force induced by variation of rotational speed of the optical disk drive. The centrifugal force is proportional to square of angular velocity such that the gap between the annulus magnet and the annulus yoke is accordingly adjustable. Variable clamping force is thus achieved by variation of the gap.