Abstract: A clamping device of a disk drive including a driving source, a driving member rotated by the driving force of the driving source; a clamping member for clamping a disk while being ascended and descended by virtue of a rotation movement of the driving member; a clamping member ascending and descending unit for switching the rotation movement of the driving source to ascending and descending movement of the clamping member, and elastically supporting the disk on a turntable while the disk is being mounted on the turntable; and an elastic press member installed on the upper surface of the driving member, for pressing the clamping member in the direction where the disk is positioned. The elastic support arm, which is thin and has a desirable restoring force, is driven by the rotation movement of the clamp driving member, thereby ascending and descending the clamper. Thus, the overall construction is thin, light and small as well as ensuring the firm and reliable clamping of the disk.