The quantification of phenomena presented by the shoreline changes and the prediction of future changes of shoreline are investigated by using a numerical model in this study. Shoreline has been sucessively affected by the activities of reclamation to maximize the land use and it also has been changed with cycles of accumulation and erosion of deposits. Many researches were performed on the jetties constructed to protect facilities adjacent to the shore. However, few studies on a seawall of protecting the beach, being very important in terms of land use, were carried out. Therefore, this study is to analyze effects of a straight seawall to shoreline changes.