There are many falling accidents of elderly people. The main reason of these accidents is that their muscle of lower limb weaken with aging. The purpose of this research is to provide them an assisting robot that can support their weight. As the robot consists of belt and rotational motor, adjusting to subject and subject's posture is easy. Thanks to the structure, hip and knee joints' extensor torques are generated by the belt pulling up when the motor rotates. We also created an evaluation apparatus that simulates human lower limb with pulleys and links to conduct an experiment. In this paper, we consider when to assist during stance phase of walking, and the experiment was conducted in order to confirm whether the apparatus follows the motion equations. Experimental results show that there are some error between calculated force and measured force. This error may be resulted from friction between belt and pulleys.