To prevent machining failure such as cracking, wrinkling, and buckling in a first neck portion by shortening the length of the first neck portion and facilitating diameter decreasing machining of the first neck portion, in a connecting structure arranging an inner pipe in an outer pipe and slidably providing one end portion of the inner pipe in the first neck portion side of the outer pipe.

The inner pipe 3 is arranged so as to project out an inner pipe end portion 3b from at least the first neck portion 2b of the outer pipe 2. A shock absorber 8 is arranged on the periphery of the projecting inner pipe end portion 3e, and the inner pipe end portion 3e is slidably fitted in the exhaust pipe 7. The first neck portion 2b of the outer pipe 2 and the exhaust pipe 7 are adhered to each other.