PURPOSE: To improve the ignitability and the rising characteristic of the titled apparatus at the time of combustion by a method wherein when the apparatus is provided with a ceramic plate having a number of small holes through which a vaporized liquid fuel is injected for ignition, a burner for heating the ceramic plate is provided.

CONSTITUTION: In case liquid fuel is burned, the fuel is supplied into an auxiliary vaporization chamber 23 which is heated by a heater 20, through a fuel changeover valve 26 and a supply pipe 25 so as to vaporize the fuel and at the same time, combustion air is introduced into the vaporization chamber 23 through an air flow changeover valve 31 so that a gas mixture is produced in the chamber 23. The gas mixture thus produced is ignited by being injected from slit-like flame ports 38 of the heating burner to generate auxiliary flames 40 and the ceramic plate 36 arranged above the flame ports 38 and forming a flame port member 37 is heated by the flames 40 quickly. Then the changeover valves 26 and 31 are turned on the side of a main vaporization chamber 22 and the gas mixture in the chamber 22 is injected into a flame port member 37 through small holes 35 for ignition to thereby perform ordinary combustion.