PURPOSE: To increase the amount of steam generation and enhance the thermal efficiency of a gas turbine of such a structure that stator blades, rotor blades, and a turbine support are cooled by water by allowing the water having cooled turbine components to pass through a deaerator and be supplied to an exhaust heat recovery boiler.

CONSTITUTION: A pure water 29 is divided into two systems-one is used in cooling the stator blades 5 and rotor blades 6 while the other is used to cool a turbine support 7 and a lubricating oil cooler 8, and the cooling water after finishing its work is allowed to flow into the lower part of an exhaust duct 12. The cooling water is passed through a gap formed between an inner and an outer iron plate of the duct 12 so that the thermal affection of the exhaust gas 11 in the duct 12 is lessened. Then the pure water (boiler feed water) discharged from the duct 11 on the inlet side of an exhaust heat recovery boiler 20 is converged with the boiler feed water from the stator blades 5 and rotor blades 6, brought in contact with a deaerating steam 27 in a deaerator 28, and sent to the exhaust heat recovery boiler 20 via a water supply tank 21 for use in generation of steam.