This paper describes the conceptual design of new robot hand by type synthesis. The conventional robot hands with rotational movement have bad controllability because the distance between the final rotational joint and the center of things grasped is changed according to the size of things grasped. This paper uses the systematic procedure of type synthesis and the knowledge for designing robot hands. The new 6-bar Watt I type conceptual robot hand with rectilinear translational movement is proposed.