PURPOSE: To enable execution of complete combustion, by a method wherein a wick is formed in a double structure state, high boiling point fuel is fed to an outer wick on the flame side, and supplying low boiling point fuel to an inner core.

CONSTITUTION: A wick forms a double of an outer wick 13 and an inner wick 12, and when the outer wick 13 is directed to the flame side, the temperature of the outer wick 13 near flame is increased over that of the inner core 12. Thus, kerosene 10 is absorbed in the outer wick 13 on the high temperature side, and methanol 17 in the inner wick 12 to form a porous wick. Through regulation of the positions of the outer wick 13 and the inner wick 12 to make flame approached the outer wick 13 to simultaneously gasify and mix the kerosene 10 and the methanol 17, which have a different boiling point from each other, at a specified width. By using a oxidation catalyst 4, air is caused to outgo from a gas distribution chamber 5 to the surface of the catalyst oxidation 4, and by imparting heat, generated by combustion reaction on the surface of the oxidation catalyst 4 by means of the air, to the outer and inner wicks 13 and 12, the kerosene 10 and the methanole 17 are gasified. This gasification enables execution of excellent combustion by compensating for a time lag and incomplete combustion during the starting of combustion of the kerosene through mixing of methanol.