A turbine cooling apparatus comprising a turbine disk having a plurality of moving blades, a torque tube coupled coaxially to one surface side of the turbine disk and having a thick stepped inner wall portion in the central portion thereof, an air separator fitted on the torque tube with the inner surface thereof in contact with the outer surface of the torque tube so that a passage through which cooling air is supplied to the moving blades via the turbine disk is defined between the air separator and the torque tube, and a torque tube cooling hollow portion provided along and in the vicinity of the outer surface of the thick stepped wall portion of the torque tube.