Gas turbine and operating method thereof

A gas turbine that supplies combustion gas generated by supplying fuel to a combustor where the fuel is combusted with compressed air compressed at a compressor to a turbine to acquire rotational power, the gas turbine comprising pressurizing means connected to a branching channel branching from a discharge-side channel of the compressor and capable of carrying out an operation for introducing and pressurizing a temperature-control medium independently from the compressor, a temperature-control-medium supply channel that guides pressurized temperature-control medium pressurized at the pressuring means to a turbine-cooling-medium channel provided in a stationary component of the turbine, and a temperature-control medium return channel that guides the pressurized temperature-control medium that has passed through the turbine-cooling-medium channel to the discharge-side channel such that the flows are combined. The pressurizing means is operated during rated operation of the gas turbine to carry out cooling by letting the pressurized temperature-control medium flow in the turbine-cooling-medium channel.