PURPOSE: To burn a large quantity of solid fuel having a low ash content over a long period of time by providing a pair of projections having a smaller vertical length than that of a gap for suction of air and vent holes which are formed in a bottom plate along the outside of the projections.

CONSTITUTION: A large quantity of solid fuel is ignited by a gas burner 13s. On the other hand, air for combustion inflowing from vent holes 29 formed in a bottom plate 21 passes over respective projections 28 to flow into a gap 19 for suction of air provided between a fuel holding member 16 and the bottom plate 21 to enter into the fuel holding member 16 through openings in a bottom surface of the fuel holding member 16 for burning the solid fuel having been ignited. The air for combustion flowing through the vent holes 29 in the bottom plate 21 is also supplied to the solid fuel held in the fuel holding member 16 through vent holes 13f, 15a provided in a heat insulating material 16. Accordingly, a large quantity of solid fuel having a low ash content can be positively burned over a long period of time.