PURPOSE: To enable the consistent and uniform burning of a solid fuel utilizing waste by a method wherein a screw axis of which feeding direction by a screw blade is directed toward a central part direction thereof is arranged on a furnace bed having approximate V-shaped section, and ash discharging ports are opened at the upper parts of the both sides of the furnace bed corresponding to the central part of the screw axis.

CONSTITUTION: A furnace bed 9 formed into approximate V-shaped section is arranged in a furnace body 2, a screw axis 11 is arranged in freely rotatable manner on the furnace bed 9 along a valley part 10 of the furnace bed 9. Screw blades 16, 16a having respectively different rotating direction with the bordering at the central part are provided in screwing manner on the outer periphery of the screw axis 11, the feeding direction by screw blades 16, 16a is directed to the central part, accordingly, a fuel is continuously pushed and supplied toward a central burning part, the burning is accelerated, also an ash is separated toward the both side directions due to the light specific gravity, the burning condition is uniformalized by continuous exposing of new burning surface. The separated ash is discharged from ash discharging ports 17, 17a opened at the both sides upper parts of the furnace bed 9 correspond to the central part of the screw axis 11.