PURPOSE: To easily cope with mis-clamping and improve efficiency in a clamp device for dividing stacked board materials, etc., by providing a movable hook and a back side hindering member on each of chucking portions having mutually opposite chucking claws.

CONSTITUTION: A cutout 8 is formed on a part of each chucking claw 4 and a movable hook 6 is provided in the cutout 8. At the time of chucking a stacked article 10 on the lowest stage only by the chucking claw 4 of one clamp 1 because of mis-clamping, the movable hook 6 of the clamp 1 holding the stacked article 10 is revolved in the directions of the arrow to release the holding and shake down the stacked article 10 onto the top of the stacked articles 9. By this structure, mis-clamping can be easily coped with, enabling accurate clamping and highly efficient dividing.