PURPOSE:To prevent unstabilized combustion such as lifting combustion and pulsating combustion at the time of ignition, by feeding air into a fuel gasifying means from an air feeding means, passing through a connecting pipe at the time of ignition only. CONSTITUTION:Gasified fuel is sucked by the sucking effect produced when an air flow is injected from an air nozzle 8. But at the time of ignition, gasified fuel, injected from a gas nozzle 7 by the air flow which is fed into a vaporizing chamber 3, is added to the aforesaid quantity of gasified fuel, passing through a connecting pipe 13. Accordingly, the sucking effect to the gasified fuel by the air flow from a burner fan 9 becomes large in comparison with the time of normal combustion. Then more gasified fuel, injected from the nozzle 7, is fed to a burner 12 passing through a mixing pipe 11. More fuel than the quantity for the time of normal combustion can be fed to the burner 12, even though some quantity condenses on its way in the pipe. With such an arrangement, stabilized combustion can be obtained if the burner 12 is cooled in low temperature, and lifting combustion and pulsating combustion can be prevented.