PURPOSE: To ensure excellent muffling performance and to facilitate manufacture and assembly by performing proper joining between the housing of a passive type muffler and an exhaust gas pipe.

CONSTITUTION: A housing 40 for a cylinder body having an opening part 40c is arranged in an acoustic wave output direction away from an acoustic wave output device 5 by a given distance, and a mounting opening 40e is formed in the side wall 40d of the housing. The outlet end part 3a of an exhaust gas pipe 3 is formed in a bent state and a flange 30 is attached to the bent part. The outlet end part 3a of the exhaust gas pipe 3 is inserted in the housing 40 through the mounting opening of the housing 40 and the flange is fixed to the housing 40.