A gas turbine comprising: a casing wall having a cylindrical shape centered at an axis and forming an outer shape of an exhaust chamber; a bearing case disposed inside the casing wall in a radial direction and supporting a bearing of a rotor; a plurality of struts installed on an outer circumferential surface of the bearing case at predetermined intervals in a circumferential direction of the bearing case and connecting the casing wall to the bearing case; an outer diffuser installed along an inner circumferential surface of the casing wall; an inner diffuser installed along the outer circumferential surface of the bearing case; a strut cover connecting the outer diffuser to the inner diffuser and covering the strut from an outer circumference side of the strut; an inflow hole installed in the casing wall for taking cooling air into the casing wall from the outside; a first flow passage formed between the casing wall and the outer diffuser and communicated with the inflow hole to allow the cooling air to flow therethrough; and a second flow passage formed between the strut and the strut cover and communicated with the first flow passage to allow the cooling air to flow therethrough; characterized in that the gas turbine further comprises: a partition wall installed between the inner diffuser and the bearing case and covering the bearing case from an outer circumference side of the bearing case; a third flow passage formed between the inner diffuser and the partition wall and communicated with the second flow passage to allow the cooling air to flow therethrough; and a flow rate adjustment device installed in at least the second flow passage. a casing wall having a cylindrical shape centered at an axis and forming an outer shape of an exhaust chamber; a bearing case disposed inside the casing wall in a radial direction and supporting a bearing of a rotor; a plurality of struts installed on an outer circumferential surface of the bearing case at predetermined intervals in a circumferential direction of the bearing case and connecting the casing wall to the bearing case; an outer diffuser installed along an inner circumferential surface of the casing wall; an inner diffuser installed along the outer circumferential surface of the bearing case; a strut cover connecting the outer diffuser to the inner diffuser and covering the strut from an outer circumference side of the strut; an inflow hole installed in the casing wall for taking cooling air into the casing wall from the outside; a first flow passage formed between the casing wall and the outer diffuser and communicated with the inflow hole to allow the cooling air to flow therethrough; and a second flow passage formed between the strut and the strut cover and communicated with the first flow passage to allow the cooling air to flow therethrough; characterized in that the gas turbine further comprises: a partition wall installed between the inner diffuser and the bearing case and covering the bearing case from an outer circumference side of the bearing case; a third flow passage formed between the inner diffuser and the partition wall and communicated with the second flow passage to allow the cooling air to flow therethrough; and a flow rate adjustment device installed in at least the second flow passage. a partition wall installed between the inner diffuser and the bearing case and covering the bearing case from an outer circumference side of the bearing case; a third flow passage formed between the inner diffuser and the partition wall and communicated with the second flow passage to allow the cooling air to flow therethrough; and a flow rate adjustment device installed in at least the second flow passage.