The first report proposed quite a new floating breakwater, the multi-body-type floating breakwater, of which transmission coefficient was proved experimentally very small compared with conventional one's. The mechanism of absorbing wave power by this breakwater was made clear by a mathematical model. Its drift force due to waves was shown small, too. So it is expected that mooring tension is also small, when it is moored by slack chains or ropes. This paper shows how small it is, comparing with conventional types. In order to estimate the mooring tension and a surging displacement of the breakwater, model experiments were carried out in irregular waves and their extreme values and others were examined and compared with theoretical calculations.