Elderly and Parkinson disease people cannot perform sit-to-stand movement properly, because they cannot smoothly move their center of mass to front by themselves. Therefore, we have been developing a sit-to-stand assistance system equipped with a moving handrail to lead elderly and Parkinson disease people to stand up from a chair. Our system consists of handrail, a six-axis force sensor, two AC servo linear actuators, frame and a personal computer. We performed sit-to-stand movement experiments of Parkinson disease people using our system. We controlled trajectory of the handrail in three different ways: curve trajectory which is based on sit-to-stand motion of the able person, forward straight line trajectory and obliquely upward straight line trajectory. We measured the center of mass, hip joint angle, and the applied force to the handrail, and evaluated the three trajectories from the view of the assistance of sit-to-stand movement. Finally, we confirmed that Parkinson disease people could stand up smoothly using our assist system.