Abstract: A muffler installed on an exhaust system of an internal combustion engine, which dissipates thermal stresses which arise from differing thermal expansions of the members comprising the muffler. The muffler comprises an outer cylinder, a pair of inner pipes, slidable into each other, penetrating into the outer cylinder and having a number of small holes therein, separators fixed to the outer cylinder by outer flanges provided with notches, and to the inner pipes by inner flanges, and the spaces defined by the inner pipes, separators and outer cylinder being filled with a sound absorbing material such as glass wool.