To improve the efficiency of a heat exchanger having a rotor cooling air cooler of a gas turbine, and a fuel heater of the gas turbine.

A tube 14 for cooling air is provided between side plates 11 and 11 of a wind tunnel 13 so that it can travel relatively to the wind tunnel 13, and both the ends of the tube 14 for cooling air are connected to a cooled air inlet header 15 and a cooled air outlet header 16. A tube 34 for fuel is provided between the side plates 31 and 31 of a wind tunnel 33 so that it can travel relatively to the wind tunnel 33, and both the ends of the tube 34 for fuel are connected to a fuel inlet header 35 and a fuel outlet header 36. Slide plates 20 and 21 that are fixed to the fuel inlet header 35 and the cooled air outlet header 16 are arranged slidably at the side plate 11, and slide plates 40 and 41 that are fixed to the fuel inlet header 35 and the fuel outlet header 36 are arranged slidably at the side plate 31.