PURPOSE: To grasp various workpieces always with fixed grasping force, by driving grasping of the workpiece with a double-finger type hand by a servo motor single drive source, so as to set a motor output torque value.

CONSTITUTION: In a control system providing in a workpiece grasping hand 10 two mutually opening/closing type grasping fingers 26, 28, performing opening/closing operation thereof by feed screw mechanisms 14, 16, driving operating these feed screw mechanisms by a servo motor Ms, and actuating the feed screw mechanisms 14, 16 by this servo motor Ms until grasping force acting in various workpieces W is generated in a fixed grasping force level, the control system is constituted such that the workpiece, with no influence by dispersing its kind and size, is grasped always by fixed proper grasping force.