Abstract
A breakwater is an important institution for protecting the property and the life of a back place from high tide or tsunami. In order to consider a design and disaster prevention planning, it is very important to evaluate appropriately the amount of subsidence in case of the earthquake of a breakwater. There is the finite element method as the technique of evaluating the amount of subsidence with sufficient accuracy. However, calculation load is large and it is unreal to verify many sections. So, this study examined the simple seismic capacity evaluation technique which changes to it. With this simple seismic capacity evaluation technique, three disaster examples etc. have been expressed.