To solve such a problem that wave energy of sea is hardly taken out as compressed air currently in order to use the wave energy for any purpose although the wave energy of sea is taken out and used as electric energy.

Wave power is taken into a bellows device in a floating body (1) as shown in Fig.(1), thereby, all devices such as a compression device are accommodated within a ship body and the power is directly transmitted to the compression device such that air can be compressed in a direction of wave rising or in a direction of wave falling. Compressed air is generated and water is once conveyed to a higher position and is stored by the conventional method. Power generation is performed with pneumatic power as much as necessary when needed. By accommodating all devices into the floating body (1), the devices are easily endured even in a severe environment on the sea and are easily maintained. By adopting a movable ship body system, response to any presumable environmental change is facilitated. Further, in the manufacturing aspect, a dock or the like of a ship yard can be used and less expenses are required.