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Various tasks are performed by upper-limbs in activities in daily living. Therefore, it is important to assist human upper-limb motions for physically weak persons such as elderly, injured, or disabled persons in order to live an independent life. To assist daily life motions of the physically weak persons, many kinds of upper-limb power-assist robots have been developed. Although the position of the center of rotation of a human shoulder joint changes with respect to the body depending on the upper-limb posture, some shoulder joint mechanisms of the power-assist exoskeleton robots do not consider the characteristics of a human shoulder joint properly. Therefore, the position difference between the center of rotation of the shoulder joint mechanism and that of a human shoulder joint might cause ill effects, so that the robot might not be able to perform the proper power-assist and a user might feel uncomfortableness. In this paper, the novel upper-limb power-assist exoskeleton robot is designed. To analyze the change of rotation axis of human shoulder joint, the displacements of the center of rotation of human shoulder joint are measured experimentally. These measurement results are used to design the novel robot that takes into consideration the characteristics of a human shoulder joint.