To provide an apparatus and method for clamping workpiece capable of clamping the workpiece without deforming the workpiece.

This workpiece clamping device includes a suction pad 1 for retaining the workpiece W, a piston 2 having the suction pad 1 at the front end and moving the workpiece W with the workpiece W retained, a case body 3 for slidably retaining the piston 2, and a retracting device 4 for retracting the piston 2 together with the workpiece W in the inner direction of the case body 3 after the piston 2 is brought into contact with the workpiece W and the workpiece W is retained while the piston 2 is protruded from the case body 3 by a predetermined amount before the workpiece W is retained. The retracting device includes an air inhalation hole 13 which is penetrated through the suction pad 1 and the piston 2, and a vacuum generator 14 which retracts the piston 2 in the inner direction of the case body by keeping the inside of the case body in a vacuum pressure state when the suction pad 1 sucks the workpiece W.