It is assumed that observed wave height and period are generally equal to significant wave height and period. About acceleration caused by rolling, pitching and yawing of the ship, we express it “the significant acceleration” due to its complexity like wave. We calculated the necessary torque to control a manual wheelchair for each wave height and compare them. If the observed wave height and the significant acceleration of the ship are known, it is possible to predict the effect of waves and so to control wheelchair behavior in advance, thereby preventing accidents on board.