The stability and function of the wave power extracting caisson breakwater are investigated experimentally with some theoretical considerations. The wave power
extracting caisson with a sloped front wall is mainly examined in the experiment. The wave power extracing caisson with the sloped front wall has a higher conversion effeciency of wave power compared with the ordinary wave power extracting caisson. The wave power extracting caisson has also advantageous functions as a breakwater caisson compared with ordinary caissons.
　Impact air pressure acts on the wave power extracting caisson when the wave surface goes below the front curtain wall of the air chamber. The impact air pressure, however, is not so large for the prototype caisson because of the scale effect of the air compression. The design method of the caisson against waves is proposed.