A combined cycle power plant is capable of improving power output and power generation efficiency by cooling intake air supplied to a gas turbine. The plant includes a gas turbine power generation system, an operating fluid power generation system, and a cooling system. The gas turbine power generation system includes an air compressor for compressing air supplied through an air incoming path, a gas turbine for generating rotary power by burning a mixture of fuel and the air compressed by the air compressor, and a first generator for generating electricity by using the rotary power of the gas turbine. The operating fluid power generation system heats an operating fluid by using combustion gas discharged from the gas turbine and generates electricity using the heated operating fluid. The cooling system cools air supplied from the air compressor by supplying the operating fluid to an upstream side of the air compressor.