For patients with muscular dystrophy, a motor dysfunction, who have difficulty operating an electric wheelchair with joysticks, a simplified one-input device is used. However, avoiding obstacles can be time-consuming. In this study, we analyzed the motor functions of the thumb of a patient with severe muscular dystrophy and identified the operations that did not cause physical fatigue. Then, we developed an operation support system to continuously operate. Finally, we conducted experiments comparing the proposed system with the conventional system and verified the effectiveness of the proposed system based on the steering accuracy of the electric wheelchair and the task completion time.