PURPOSE: To send uniformlly combustion air to a solid fuel combustion unit in a combustion device which burns both solid fuels, such as firewood, coal and waste and liquid fuels, such as gas and petroleum.

CONSTITUTION: A grate 2 is mounted in the middle part of a combustion cylinder 1 and a solid fuel combustion unit 3 is installed to the upper part of the grate 2 while a fluid fuel combustion unit 4 is installed to the lower part. A burner 5 is installed to the side wall of the fluid fuel combustion unit 4. Two ring-shaped bulkheads 8 provided with an opening 7 in the central part are mounted to the peripheral wall of the fluid fuel combustion unit 4 between the grate 2 and the burner 5, thereby communicating the bulkheads 8 with a blower 6. A slit-shaped air outlet 9, which reduces the width of the inner edge of the opening 7, is installed to the ring-shaped bulkheads 8 so that the air outlet 9 may serve to supply the combustion air fed from the blower 6 to the solid fuel combustion unit 3 uniformlly.