Abstract: (Problem) A pair of finger bodies should be able to easily sandwich a workpiece without being interfered by other adjacent workpieces, and should be able to easily and rapidly change a standby open clearance depending on an external diameter of multiple workpieces in various sizes. (Means for Solving the Problem) A pair of hand pistons connected by a connection rod is inserted in a hand cylinder, and openings are formed in the hand cylinder. A driving rack gear is formed on the connection rod, and engages with a driving pinion gear arranged on a penetrating axis rotatably arranged in the hand cylinder to penetrate the hand cylinder.