PURPOSE: To prevent declination of an outlet pipe caused at the time of coupling the same to a discharge muffler case, by disposing the outlet pipe along a coupling part of a longitudinally split muffler case, and coupling them together by way of soldering.

CONSTITUTION: A through-hole 11 is formed in one half 81 of a discharge muffler case at the root part of a flange part 151 or at the peripheral part of said one half 81 of the muffler case in the manner that it is extended longitudinally of the muffler case. An outlet pipe 12 is inserted into the through-hole 11 in the manner that its longitudinal outer peripheral part is held in contact with the flange part 151 and extends along the flange part 151 of the muffler case, and the outlet pipe 12 is fixed to the flange part 151 by way of copper soldering. Therefore, it is enabled to prevent declination of the outlet pipe 12 caused at the time of coupling the same to the muffler case and to make it unnecessary to fix the outlet pipe 12 temporarily in the through-hole 11.