an object of the present invention is to provide an exhaust muffling device having a simple structure , which is capable of suppressing air column resonance favorably , irrespective of a length of an outlet pipe of an exhaust pipe which communicates with a muffler , and with which it is possible to achieve appropriate reductions in weight and cost . the exhaust muffling device of the present invention comprises a muffler having an expansion chamber whose length is l in an exhaust direction , and an outlet pipe being in communication with the expansion chamber and whose pipe length is approximately 2nl in which n is a natural number .