To prevent an exhaust outlet from being clogged with mud by inhibiting accumulation of mud on a tail cap of a muffler device and quickly dropping the mud.

The exhaust outlet 34 is provided at the center of a rear surface 46 of the tail cap 21 closing a rear end of a muffler body, and a tail pipe 30 is connected at its rear end to the exhaust outlet 34. The exhaust outlet 34 is formed in a tail pipe supporting member 35 mounted on the rear surface 46. The tail pipe supporting member 35 is formed with an annular mud guiding recessed groove 37 opening rearward around the exhaust outlet 34. The mud dropping on the rear surface 46 is guided into the mud guiding recessed groove 37 and moved in the mud guiding recessed groove 37 owing to its capillarity. Accordingly, the mud can be moved down along the mud guiding recessed groove 37 and smoothly dropped, thus preventing the mud from accumulating on the rear surface 46 and closing the exhaust outlet 34.