Exoskeleton is an external structural mechanism with joints and links corresponding to those of the human body. It transmits torques from actuators through rigid exoskeletal links to the human joints when it is worn. We have been developing exoskeleton robots for assisting the motion of physically weak individuals such as elderly or slightly disabled in daily life. In this paper we propose a three degree of freedom (3DOF) exoskeleton robot for the forearm pronation/supination motion, wrist flexion/ extension motion and ulnar/radial deviation. The paper describes wrist anatomy toward the development of the robot, the hardware design of the exoskeleton (mechanical structure and mechanism, sensors and actuators, power transmission and safety aspects) and potential control methods. Force control using force/torque sensors located at wrist and forearm and electromyographic (EMG) signals based control using skin surface EMG signals of forearm and wrist muscles are the potential control methods for the robot. Experiments have been performed to evaluate the proposed exoskeleton.