A gripper comprises a motor 25, contained within a case 32, for driving a translational nut 23 that is moved in translation, a finger 20 having one end connected to the translational nut 23, with the other end being connected to the case 32, in which when the one end is pulled upon a movement of the translational nut, the finger is expanded in the amount of displacement at a top end, a plate-like stopper member 26 connected to one end of the finger 20 and having a projecting piece 26b around the outer periphery thereof, a holder member 22 for inserting loosely the projecting piece 26b, a locating nut 28 for adjusting a predetermined gap from the stopper member 26 by being threadingly engaged with a threaded portion of the holder member 22, and a spring 29 for pressing the locating nut 28.