Provided is a gas turbine capable of achieving high-speed startup of the gas turbine through quick operation control of an ACC system during startup of the gas turbine, improving the cooling efficiency of turbine stationary components, and quickly carrying out an operation required for cat back prevention during shutdown of the gas turbine. Included are a pressurizing device (40) connected to a branching channel (42) branching from the discharge side of a compressor (11) and capable of carrying out an operation for introducing and pressurizing air independently from the compressor (11); a temperature-control-medium supply channel (43) that guides compressed air pressurized at the pressuring device (40) to a turbine-cooling-medium channel (50) provided in stationary components of a turbine (13); and a temperature-control-medium return channel (44) that guides the compressed air that has passed through the turbine-cooling-medium channel (50) to the discharge side of the compressor (11) such that the flows are combined, and the pressurizing device (40) is operated at startup of the gas turbine and in preparation immediately before startup to carry out temperature-raising and cooling by letting the compressed air flow in the turbine-cooling-medium channel (50). The pressurizing device (40) is operated during shutdown of the gas turbine to exhaust the high-temperature gas remaining in the turbine (13).