The purpose of our research is to build a system for mutual adaptation between a user and assistive devices for restoration of motor function. To build such system, it is necessary to know human's motion patterns. In this paper, as the first step, we investigated human motion characteristic on human-machine system like EMG (electromyogram) prosthetic hand and EMG to motion classifier system. In the experiment, we measured the EMG signals and investigated a difference between motion patterns of teaching motion, i.e. user's intended motion, and that of actual motion using the proposed criteria. As results, it is clear that these criteria are useful to analyze changes of human motion patterns.