To provide a method of feeding combustion air to a gas turbine to improve the efficiency of a turbine as the turbine vane of a gas turbine is cooled.

By feeding fuel gas and combustion air to a combustor 7, fuel gas is burnt in an air insufficient state to a given temperature. The combustion gas is fed to the incoming side of the gas turbine 1 and combustion air is fed to the turbine static vanes SW2 and SW3 of the gas turbine 1 and cooled, combustion air after cooling is discharged in combustion gas in the gas turbine 1 at a velocity of flow exceeding a speed of combustion. This constitution effects slow two-stage combustion of combustion gas in a high temperature and low oxygen concentration atmosphere to restore a combustion gas temperature, and feeds the combustion gas to a subsequent stage.