When supporting standing-up motion, a caregiver takes advantage of gravity force to make sufficient momentum without bearing heavy burden. The physical abilities or decisionmaking abilities decrease for many of elderly people who need care. We propose a self-help standing-up method for such people. The method with quasi-static motion in which the acceleration is approximated to zero, so as to keep safety at the time of emergency, is preferable. However, the quasi-static motion gives heavy burden to a caregiver because it cannot make efficient use of inertia force by the help of gravity force. Compared to human assist, mechanical system can easily realize the quasi-static motion, since a mechanical system has an ability to hold a large force. However, a quasi-static motion trajectory has to be newlydeveloped because it is not well known. Therefore, we propose the mechanical system and a quasi-static method for supporting standing-up motion. As an example, the method using artificial upper body constraint, and fitted to physical characteristics of each patient have been proposed. This system is found to be the effectiveness.