In the aging society, more effective rehabilitation/welfare instruments to support seniors and disabled persons are required. However, it becomes difficult the evaluation of such instruments for safety reasons. Therefore, we suggest the use of a humanoid robot, which is able to display human motions, instead of a human to evaluate such instruments as an experimental subject. The use of robots for measurement purposes is safe and gives us the quantitative data for improving rehabilitation/ welfare instruments. Recently, we have developed the new humanoid robot as a human motion simulator, WABIAN-2. This robot can walk autonomously with the knees stretched like a human by using waist motion, and also it can walk by physically interacting with a walk-assist machine. In this paper, the experiments are focused verifying if the WABAIN-2 can be considered as a human motion simulator to move a walk-assist machine while walking.