Development of a device system to extract the ocean wave energy was discussed in this paper. The new facility of wave energy converter called a water-chamber-type seawall has been tested to examine the performance as a wave power extraction device as well as a wave dissipater. The water-chamber-type seawall has a similar structure to the wave energy converter of OWC type (Oscillating Water Column). Wave power is extracted by a water turbine which installed in the chamber. In order to improve the efficiency of wave energy conversion, an axisymmetric guide vane device was applied to accelerate the water turbine of Savonius type. It was observed experimentally that the wave energy conversion efficiency of the proposed seawall is about 18% at maximum. The seawall of this type, however, has another function, such as a wave reflection dissipater. It was also confirmed that the reflection coefficient of the water-chamber-type seawall is about 0.5 in average.