We have developed a rehabilitation training system called the Useful and Ultimate Rehabilitation System PARKO (UR System PARKO) to promote the recovery of motor function of the severe chronic plegic hand of stroke patients. This system was equipped with two functions to realize two conditions: (1) fixing of all fingers to a hyperextended position and (2) extending the elbow joint while applying resistance load to the fingertips. A clinical test was conducted with two patients to determine the therapeutic effect of the UR System PARKO for severe plegic hand. In both patients, the active ranges of motion of finger extension improved after training with the UR System PARKO. Moreover, the Modified Ashworth scale scores of finger extension increased. Thus, training reduced the spastic paralysis. These results suggest the effectiveness of training with the UR System PARKO for recovery of motor function as reflected in the finger extension of the severe plegic hand.