Provided is a gas turbine apparatus including: a turbine unit comprising an output shaft; a cooling gas generation unit, comprising a rotation shaft, which receives power from the output shaft through the rotation shaft and generates a compressed cooling gas; a first duct unit which transfers the generated compressed cooling gas to the turbine unit; a clutch unit which controls a power transfer connection between the output shaft and the rotation shaft; and a control unit which controls the transferring of the generated compressed cooling gas.