A flotation system for an offshore power generation platform, the system being used in offshore wind power generation and the like and comprising: multiple buoyant bodies each containing a high-pressure air and ballast water therein to create buoyancy; connecting members connecting the multiple buoyant bodies and a platform to each other, the platform on which a power generation facility is provided; ballast water flowing tubes connecting the multiple buoyant bodies to allow the ballast water contained in the multiple buoyant bodies to flow between the multiple buoyant bodies; and an equilibrium sensor sensing an equilibrium state of each of the multiple buoyant bodies and transmitting a signal, characterized by further comprising: a pressure sensor sensing pressure present in each of the multiple buoyant bodies and transmitting a signal; a high-pressure tank supplying the high-pressure air into the multiple buoyant bodies; a compressor replenishing air pressure present in the high-pressure tank; and a controller controlling, in response to the signals from the equilibrium sensor and the pressure sensor, an amount of air supplied from the high-pressure tank to the buoyant body where the buoyancy is required to increase and an amount of air discharged from the buoyant body where the buoyancy is required to decrease to outside, wherein the controller, when a signal is received from the equilibrium sensor, the signal indicating that one of the multiple buoyant bodies is relatively lowered than a different one of the buoyant bodies and thus equilibrium therebetween is upset, estimates the pressure present in the one of the buoyant bodies to supply the high-pressure air thereinto until the estimated pressure is reached, causing the ballast water contained in the one of the buoyant bodies to flow into the different one of the buoyant bodies, the controller estimating the pressure present in the different one of the buoyant bodies into which the ballast water is introduced to discharge the high-pressure air therefrom until the estimated pressure is reached, whereby the equilibrium between the multiple buoyant bodies is maintained. multiple buoyant bodies each containing a high-pressure air and ballast water therein to create buoyancy; connecting members connecting the multiple buoyant bodies and a platform to each other, the platform on which a power generation facility is provided; ballast water flowing tubes connecting the multiple buoyant bodies to allow the ballast water contained in the multiple buoyant bodies to flow between the multiple buoyant bodies; and an equilibrium sensor sensing an equilibrium state of each of the multiple buoyant bodies and transmitting a signal, characterized by further comprising: a pressure sensor sensing pressure present in each of the multiple buoyant bodies and transmitting a signal; a high-pressure tank supplying the high-pressure air into the multiple buoyant bodies; a compressor replenishing air pressure present in the high-pressure tank; and a controller controlling, in response to the signals from the equilibrium sensor and the pressure sensor, an amount of air supplied from the high-pressure tank to the buoyant body where the buoyancy is required to increase and an amount of air discharged from the buoyant body where the buoyancy is required to decrease to outside, wherein the controller, when a signal is received from the equilibrium sensor, the signal indicating that one of the multiple buoyant bodies is relatively lowered than a different one of the buoyant bodies and thus equilibrium therebetween is upset, estimates the pressure present in the one of the buoyant bodies to supply the high-pressure air thereinto until the estimated pressure is reached, causing the ballast water contained in the one of the buoyant bodies to flow into the different one of the buoyant bodies, the controller estimating the pressure present in the different one of the buoyant bodies into which the ballast water is introduced to discharge the high-pressure air therefrom until the estimated pressure is reached, whereby the equilibrium between the multiple buoyant bodies is maintained.