A gas turbine configured to prevent eccentricity of a rotor (14) due to heat is installed with a strut (23), an outer diffuser (24), an inner diffuser (25), a strut cover (26), and a partition wall (28), wherein the gas turbine includes an inflow hole (31) for cooling air (W), a first flow passage (R1) formed between a casing wall (21) and the outer diffuser (24), a second flow passage (R2) formed between the strut (23) and the strut cover (26), a third flow passage (R3) formed between the inner diffuser (25) and the partition wall (28), and an outflow hole (51) installed in the inner diffuser (25).