The characteristics of swell are estimated by using the observed wave height data classified by wave period range in NOWPHAS (Nationwide Ocean Wave information network for Ports and HarbourS). Estimated characteristics demonstrate that the direction of swell is approximately derived by using the location of typhoon. As a result of directional spectrum analysis, the design condition for swell are expressed as JONSWAP spectrum with wave angle spreading parameter Smax = 50 ~ 75.