The purpose of this study is to develop the supporting system for standing up and sitting down of the elderly people. The feature of the supporting system is to assist the human motion for standing and sitting without any sensors attached to the people. First of all, we measured a human motion of standing by the force plate and a force sensor. As the result, we clarified the feature of a human standing motion. On the basis of the feature, we considered the design guideline of the supporting system. And we made the motion simulator to estimate a human posture during the stand-up motion from the force plate and force sensor data.