PURPOSE: To make fitting between an inner cylinder of a combustor and a transition piece reliable, by a method wherein a spring having elasticity in a circumferential and radial directions is formed by making a cylindrical spring into an annular state, which is fitted in the inner cylinder of the combustor, the rings are inserted on an upstream and down stream sides of the spring and it is so comstituted that the annular spring is turned between the rings in an axial direction.

CONSTITUTION: Stop rings 22a, 22b are fixed to an external circumference of a downstream end part 21 of an inner cylinder 20 of a combustor. Positions of the stop rings 22a, 22b in an axial direction have been fixed by an insertion margine between a transition piece 23 and the inner cylinder 20 of the combustor, the upstream side stop ring 22a is positioned in the vicinity of an inlet part 23a of the transition piece 23 and the downstream side stop ring 22b is provided in the vicinity of a downstream end part 21 of the inner cylinder 20 of the combustor. Thicknesses of the stop rings 22a, 22b are made into ones of about a half of a gap between the transition piece 23 and the inner cylinder 20 of the combustor, and it is so constituted that excessive wear or deformation and further disconnection of the annular spring 24 do not occur.