The invention provides a gas turbine combined cycle structured such that an intermediate cooling device for cooling a compression air discharged from a low pressure compressor, so as to reduce a load of a high pressure compressor, is provided. The gas turbine combined cycle in accordance with the invention is structured such as to branch water from a condenser to a steam generating device for generating steam. Exhaust gas discharged from a steam turbine is condensed to water. Compression air discharged from a low pressure compressor is cooled by being supplied to an intermediate cooling device, and is then supplied to a high pressure compressor. Steam which heats and operates the steam turbine is generated by the heat recovered by the cooling of the compression air in the intermediate cooling device. Accordingly, there can be obtained a gas turbine combined cycle having the advantage of the conventional intermediate cooling type gas turbine combined cycle, but exhibiting an improved combined efficiency.