To obtain a muffler which is effective against exhaust sound including a wide frequency band.

A conical porous cylindrical member 6 wherein a large number of small holes are bored on the whole of its cylinder wall is provided in a main body case 2 of the muffler. Exhaust gas flowing from an entrance pipe 1 is made to circulate into the main body case 2 on the outside through the small holes 7 arranged in conical shapes on the cylindrical member 6. At that time, resonance sound having a wide frequency band is generated from each small hole 7, thereby canceling the exhaust sound.