A workpiece cradle and a clamp arm is provided, and an arm opening/closing cylinder 15 for opening and closing the clamp arm and the workpiece cradle are attached to a moving block 13. To a workpiece-cradle driving cylinder 23 provided with a piston rod 25 for driving the moving block 13, fluid is supplied from workpiece-cradle driving supply/discharge ports 27a and 27b formed in a manifold block 21. To the moving block 13, guide rods 33a and 33b are fixed and, to the arm opening/closing cylinder 15, fluid is supplied, from arm driving supply/discharge ports 34a and 34b formed in the manifold block 21, via hollow holes 36a and 36b in the guide rods 33a and 33b and via fluid supply/discharge paths 43a and 43b in the moving block 13.