A brush seal assembly for a gas turbine, comprising: a brush seal disposed around an outer circumferential surface of a rotating body rotated inside a casing and oriented with respect to a rotating direction of the rotating body , the brush seal having a multitude of bristles forming an angle with respect to a radial direction of the rotating body ; a brush support portion configured to support the brush seal by extending toward the rotating body while contacting a low-pressure side of the brush seal , wherein the low-pressure side of the brush seal is an axially rear side of the brush seal ; and an assembly support portion configured to support the brush seal and the brush support portion and to receive respectively a base end of the brush seal and an axial protrusion of the brush support portion , wherein the assembly support portion includes: a first support ; a second support configured to support the brush support portion from an axially rear side of the brush support portion opposite to the contact with the brush seal ; and a third support disposed between the first and second supports to jointly support the brush seal and the brush support portion ; characterized in that the brush seal assembly further comprises a first fluid space (S1) formed between the brush seal and the first support facing the brush seal , and wherein the brush support portion comprises a plurality of inclined plates respectively extending toward the rotating body , and a second fluid space (S2) is formed between the brush support portion and the second support facing the brush support portion . a brush seal disposed around an outer circumferential surface of a rotating body rotated inside a casing and oriented with respect to a rotating direction of the rotating body , the brush seal having a multitude of bristles forming an angle with respect to a radial direction of the rotating body ; a brush support portion configured to support the brush seal by extending toward the rotating body while contacting a low-pressure side of the brush seal , wherein the low-pressure side of the brush seal is an axially rear side of the brush seal ; and an assembly support portion configured to support the brush seal and the brush support portion and to receive respectively a base end of the brush seal and an axial protrusion of the brush support portion , wherein the assembly support portion includes: a first support ; a second support configured to support the brush support portion from an axially rear side of the brush support portion opposite to the contact with the brush seal ; and a third support disposed between the first and second supports to jointly support the brush seal and the brush support portion ; characterized in that the brush seal assembly further comprises a first fluid space (S1) formed between the brush seal and the first support facing the brush seal , and wherein the brush support portion comprises a plurality of inclined plates respectively extending toward the rotating body , and a second fluid space (S2) is formed between the brush support portion and the second support facing the brush support portion . a first support ; a second support configured to support the brush support portion from an axially rear side of the brush support portion opposite to the contact with the brush seal ; and a third support disposed between the first and second supports to jointly support the brush seal and the brush support portion ; the brush seal assembly further comprises a first fluid space (S1) formed between the brush seal and the first support facing the brush seal , and wherein the brush support portion comprises a plurality of inclined plates respectively extending toward the rotating body , and a second fluid space (S2) is formed between the brush support portion and the second support facing the brush support portion . <EOS>