A loss of heat that can be recovered in a heat recovery steam generator is eliminated, whereby a combined cycle electric power generation plant with high heat recovery efficiency is provided. A combined cycle electric power generation plant is adopted that includes a heat recovery steam generator 30 that generates steam for driving a steam turbine 20 using heat of exhaust gas of a gas turbine 10, a cooling air cooler 71 that causes high-pressure feed water supplied from a low-pressure economizer 37 of the heat recovery steam generator 30 and compressed air for turbine cooling extracted from a compressor 11 of the gas turbine 10 to perform heat exchange to heat the high-pressure feed water to thereby cool the compressed air, and a fuel gas heater 72 that causes the compressed air cooled in the cooling air cooler 71 and a fuel gas of the gas turbine 10 to perform heat exchange to further cool the compressed air to thereby heat the fuel gas.