To solve the problem of damaging the environment due to noises released from an exhaust stack.

This exhaust stack is provided with a muffling body 3 to the upper part of an exhaust guide port 21 facing an exhaust passage 12, the muffling body 3 being formed by shape-retaining porous granules and powder 31 made of perlite in massive form with maintaining air permeability, and muffling layers 44 are laminated and constructed on the peripheral wall surface of the exhaust passage 12, the muffling layer being formed by shape-retaining porous granules and powder made of perlite in laminar form with maintaining air permeability. The muffling bodies 3 are arranged on a plurality of places in the exhaust gas flow direction inside the exhaust passage 12, and a lower part muffling layer 5 is arranged on the lower part of the exhaust guide port 21, the lower part muffling layer 5 being formed by shape-retaining porous granules and powder made of perlite in laminar form.