To realize a high-output wave activated power generation buoy in which high output can be gained based on a small-sized buoy moored on the ocean, power unit price per output is extremely low, and control of over-input from stormy wave is rationally possible compared to a conventional highly efficient wave activated power generating device having obtained energy from motion of a buoy in relative to a fixed member.

A quasi sealed water chamber containing a large amount of sea water in a base buoy as an ocean station is provided, a natural vibration cycle of the base buoy is prolonged by using a large mass addition effect of this sea water for phase lag, and a new power generation method is obtained for high-output wave activated power generation from a relative motion with a short cycle buoy with a small phase lag and a short natural vibration cycle. By providing a difference in the horizontal cross section of a float chamber between a normal wave with small wave height and a stormy wave with high wave height, a large difference is generated in a buoyancy change by wave, and rational control on over-input is realized by considerably compressing the phase lag of the base buoy at a storm.