A combustion duct assembly for a gas turbine includes a liner, an annular spring seal and a transition piece. The annular spring seal is outwardly convex and coupled to an outer face of the downstream side of the liner. The transition piece has includes an inner wall and an outer wall that surrounds the inner wall. The convex part of annular spring seal is operable to elastically engage the inner wall of the transition piece. An end portion of the downstream side of the annular spring seal is fixed to the line. The annular spring seal includes a plurality of through holes formed in an upstream side of a point where the annular spring seal comes into contact with the inner wall. The liner includes a plurality of vent holes formed in an inner area surrounded by the spring seal.