PURPOSE: To obtain a complete combustion of exhaust smoke by generating a complusive exhaust smoke and a natural convection by means of an exhaust smoke cylinder and a multistage throttle within the firewood stove having a double-chambered structure of a combustion chamber and a heat insulating chamber located outside the combustion chamber.

CONSTITUTION: Outside the combustion chamber 1 is located the heat insulating chamber 9 which includes an interrupting means 10 and has the exhaust smoke cylinder 11 leading to a chimney 5. Below the combustion chamber 1, fire-grates 12 and 14 are arranged which respectively has a plurality of exhaust smoke holes 13 and 15. The exhaust smoke holes 13 are arranged at an interval wider than that at which the exhaust smoke holes 15 are arranged, and these holes are not aligned with each other. With an interrupting means 4 of an exhaust smoke cylinder 6 and an interrupting means 7 of an air inlet cylinder 8 kept open, and with the interrupting means 10 kept closed, a pilot flame is put through an inlet port 20 for firing. Then the interrupting means 4 is turned to be closed and the interrupting means 10 is turned to be open, so that the exhaust smoke is forced to enter the heat insulating chamber through the fire-grates 12 and 14 and further to pass through the exhaust smoke cylinder 11 into the chimney 5. During this passing through such a path, due to the alternate arrangement of the exhaust smoke holes 13 and 15, any remaining fire burns out. In addition, since the fire-grates 12 and 14 become very hot at this time, the exhaust smoke passing therethrough can be burned completely. This exhaust smoke enters the heat insulating chamber 9 via a ventilation hole 16 so as to generate a natural convenction therein and then compulsively introduced into the chimney 5 through the exhaust smoke cylinder 11.