In recent trends of popularized sports and increased industrial hazards, we need the therapeutic modality in clinical setting, as a training and testing device for sports practicians, and as a method for scientific examination of post-operative status of muscles and joint function for orthopedist. Isokinetic exercise with Cybex II overcomes many biomechanical factors and can be used for fatigued patients by control of resistance. We examined internal rotator and external rotator muscle force of the shoulder joint, in order to acquire the isokinetic normative data of the shoulder for clinical use. The result were as follows 1. Strength and Power decreased as ages getting old, and there was significantdiminishbetween5th decade and 6th decade. 2. Power endurance did not decrease significantly as ages getting old. 3. The mean values of strength and power in internal rotator were higher than external rotator.