Recently, ocean energy has attracted attention as the renewable energy that can generate electricity all the time regardless the weather condition. Thus, we developed the basic structure of tidal current power generation equipment. However we found the following problems. The currents of tide at high tide and low tide are opposite each other. Thus, the blade of water turbine made a straight line. However, the generated electric power is lower than the curved blades. In order to solve the above problems, it was possible to select optimum shape of blades and provide the auxiliary buoyant body to confirm the appropriate waterline position of water turbine.