PURPOSE: To clamp varuous-sized panels by simultaneously moving oppositely arranged two clamp claws to clamp them by energizing force of a spring in the opposite direction by a driving means and a link mechanism.

CONSTITUTION: When a cylinder 7 is actuated and moves a slide shaft 3B in the A direction, simultaneously when a claw support block 8B is moved in the A direction, a claw support block 8A is moved in the A' direction in the inverse direction of A through a connecting plate 12B, a rotary plate 11 and a connecting plate 12A. Thereby, clamp claws 13A and 13B fixed to the blocks 8A and 8B are moved in the opening direction against energizing force of a spring 6. Then, when panels 20 are placed between the claws 13A and 13B, an actuating rod of the cylinder 7 draws back, and moves a link mechanism in the inverse direction of A by the energizing force of the spring 6, and various- sized panels 20 can be clamped by the claws 13A and 13B.