A part of authors have made some studies on wave exciting forces on large floating structures composed of multiple body elements for ocean space utilaization such as floating airport, taking hydrodynamic interaction into accout. In the previous paper, some characteristics of interaction effects from computed results were reported, including the followings: 1) Peaks of response function of wave exciting force of inner body elements are larger than of outer ones. 2) There is a kind of singular frequency where wave exciting force of body elements in head sea condition reach six times as high as that of a single body as a result of interaction effects. Model experimental results are shown and two points above are confirmed in this paper. It is proved from both experimental and computed results that at the singular frequency there appears standing wave. It is also discussed that the singular frequencies appear only in head sea condition.