PURPOSE: To enable automatical clamping in a short time by detecting the delivery of a workpiece to operate a clamp and detecting the contact of an upper-side clamp with the workpiece and the rise of a lower-side clamp to move one support in a cross direction of the workpiece.

CONSTITUTION: When the end face of a workpiece which is delivered between supports has contact with a stopper, that is detected by workpiece detecting means LS1, LS2 to drive and control corresponding clamp driving means 31a, 31b through a control means 61 which inputs detection signals therefrom. This drive results in an upper-side clamp lowered by clamp mechanism 23a, 23b, put in contact with the workpiece, restricted in lowering and then raised. That is detected by lower-side clamp detecting means LS3, LS4, and by the control means 61 which inputs at least either one of detection signals therefrom, a crosswise driving means 14 is driven and controlled to move one support in such a direction that the workpiece in a cross direction is clamped.