PROBLEM TO BE SOLVED: To provide an efficient method of taking out wave energy.SOLUTION: Containers are sunk in water at different water levels in depth order with the container 1 at the shallowest and container 4 at the deepest. An air is allowed to flow only in a direction from the container 1 to the container 4. The pressure that the containers 1 to 4 receive in the absence of water column pressure by waves is the pressure at the depth of water and stationary pressure. The containers 1 to 4 receive higher stationary pressure in order, and the air pressure in a container is balanced with the stationary pressure. Here, when waves occur on the water surface, pressure varying with time is generated in the water. Pressure applied to each of the containers at a moment is different in intensity and direction, and when the total of stationary pressure that the container 2 receives and underwater pressure by the waves is smaller than the total of stationary pressure that the container 1 receives and underwater pres
