PURPOSE: To perform a treatment by a steady combustion through the production of a normally steady flame, by a method wherein a combustion chamber, formed with a space expanding toward the outside at a specified widening angle, is provided in a periphery positioned inside of secondary oxygen jet holes in an oxygen nozzle at a tip of a fuel atomizing nozzle.

CONSTITUTION: A combustion chamber 22, formed with a space widening toward the outside at a widening angle α of 60W120°, is formed in a periphery located inside of secondary oxygen jet holes 18 in an oxygen jet nozzle 14 at a tip of a fuel atomizing nozzle 12. The depth of the combustion chamber 22, or distance l between a tip 14a of the oxygen jet nozzle 14 and a tip 12a of the liquid fuel jet nozzle 12 is set to 1/10W1/2 a diameter (d) of the periphery on which the secondary oxygen jet hole 18, formed in the oxygen jet nozzle 14, are arranged. Even in a heat-fusing incinerator where a contamination is produced by a heat-fusion and incinerating process, this constitution prevents drawing of contaminants into a nozzle part, which results in preventing such contaminants from causing condensation or coagulation at the nozzle part and in generating a normally steady flame, and this permits the further improvement of a combustion performance.