PURPOSE: For completely preventing the deposition of tar and carbon and improving combustion and combustion load performances of a gasifying combustor, to keep the temperature of the range between a gasifying reaction pipe and the outlet of a burner above 200°C.

CONSTITUTION: A liquid fuel introducing pipe 6, a water introducing pipe 7 and a primary air feeding pipe 8 for a cylindrical reaction pipe 4 are attached on one end of the boiler drum 3 having an inner drum 1 and an outer drum 2 both cylin- drical for example, and a heating chamber 9 for heating primary air for example forward of said reaction pipe 4. Further, a narrow pipe is placed so as to extend between the tip of said reaction pipe 4 and a burner through said boiler drum 3 and position at the center of the inside of a secondary air feeding pipe 11, and a propane gas introducing pipe 12, a stabilizer 13 and a flame outlet 14 are provided on said secondary air feeding pipe 11 for initial preheating of said reaction pipe 4. During the operation of said reaction pipe 4, the temperature of the range between said reaction pipe 4 and the outlet of said burner is kept above 200°C.