To efficiently remove SO2 and NOx incorporated in exhaust gas of a light oil machine by filling active coal in a space between a filter inner layer cylinder part and a filter outer layer cylinder part, and providing an exhaust gas introduction and discharge cylinder inside an inner space of the filter inner layer cylinder part.

Respective flanges of a muffler 1, an exhaust gas cylinder 2 and a discharge cylinder 3 are tightened with bolts and nuts. The metallic exhaust gas introduction and discharge cylinder 4 is constituted of a porous cylinder 4a whose end is opened and whose cylinder wall 4a1 is pored with plural fine holes 4a2 with 9 mm diameter and also the cylinder part 4b in which a lot of fine holes with 3 mm diameter are pored on the back end part 4a3 and whose front end is connected to the back end 4a and in which plural gas vent holes 4b1 are pored on the back end part cylinder wall and a closing plate 4b2 are provided on the back end. The porous cylinder part 4a is formed with a flange 4a5 at nearly a central part in the longitudinal direction of the cylinder and the flange 4a5 is fixed to a flange of the muffler 1 by tightening with bolts and nuts, etc. The exhaust gas flows in as shown by the arrow and diffuses into an activated carbon layer 6.