This paper deals with the response analysis of a floating building structure subject to both wind and wave loads. The hydrodynamic analysis is performed with sets of wind and wave loads selected from the 100-year return period concept to assess the effect of extreme ocean environmental loads on a floating building. From hydrodynamic analysis in time-domain analysis, it is shown that the responses obtained from the analysis in consideration of both wind and wave loads are far greater than those of wave load only.