Cooling structure of combustor tail tube

To present a cooling structure of combustor tail tube capable of avoiding formation of cracks in the tail tube by lessening thermal stress and preventing thermal deformation, and extending the service life, the invention provides a cooling structure of combustor tail tube forming a multiplicity of cooling jackets (5) extending in the longitudinal direction of tail tube of a gas turbine combustor along the entire circumference of the tail tube wall, in which passage sectional area of the cooling jackets (5) is varied depending on the metal temperature of parts of the tail tube (4), for example, the passage sectional area of the cooling jackets (5) formed at the rotor side wall and the mutually opposite side walls of the adjacent tail tube is formed larger than the passage sectional area of the cooling jackets (5) formed at the casing side wall.