When we evaluate the safety of activity on a floating pier or a small ship, it is important to know the characteristics of motions in ship waves. Because when ship waves come to a floating body, the motions become large unexpectedly. The main purpose of this study is to investigate the characteristics of ship motions in waves generated by a high-speed boat passing near the mooring small floating body. Ship motions in ship waves are measured by the field tests, the short period maximum motions are also investigated by the approximate calculations.