Abstract: A heat engine is provided that can improve thermal efficiency of a gas turbine . When gas such as air enters a compressor C101 of a gas turbine apparatus 100 (state 1), the gas becomes high-temperature gas by a combustor B102 (state 3) and moves toward a turbine T103. Another turbine T104 is placed at the back portion of the turbine T103 where air of state 3 enters, the gas enters a first heat exchanger Hx 105 (state 4) and is supplied to a compressor C109 (state 5). Thereafter, the supplied gas is discharged from a compressor C112 (state 12) through a heat exchanger Hx106 of an intercooling portion 151, a compressor C110, a heat exchanger Hx107, a compressor C111, and a heat exchanger Hx108 (states 6 to 11).