An apparatus for clamping both large and small disks is provided, including a disk tray inside a base, an upper case and two clamping mechanisms above the disk tray and the base. Each clamping mechanism includes a slider and a gripper structure. The gripper structure further includes a first gripper, a second gripper, and a resilient element located between the first and the second grippers. The second gripper includes a first belt-ring and a second belt-ring. When the disk is loaded, under the force of the resilient element, the first belt-ring and the second belt-ring hold the disk onto the disk tray firmly. When the first gripper moves to a specific position of the groove on the upper case, the first gripper causes the second gripper to rotate so that the resilient element stops to exert the force. Hence, the first belt-ring and the second belt-ring rotate upwards so as to complete the loading process. On the other hand, to eject a disk, the resilient element re-exerts force on the first gripper to cause the first belt-ring and the second belt-ring to rotate downwards to hold the disk until the disk is completely ejected to complete the ejecting process.