PURPOSE: To prevent blow off of flame and to stabilize distribution of flame, by a method wherein an evaporating device is disposed to the one end part of a combustion cylinder, a combustion gas exhaust port is formed in the other end part, and an air introduction hole formed in a combustion cylinder is inclined in the direction of an exhaust port.

CONSTITUTION: An evaporating device 2, with which an evaporating chamber 7 is formed, is disposed to the one end part of a combustion cylinder 11 with which a combustion chamber 5 is formed, a combustion gas exhaust port 13 is formed in the other end part, and an air introduction hole 17 is formed in a manner to be inclined in the direction of an exhaust port 13. Since air for combustion is prevented from collision with the production zone of flame 22 and the flow passage of air for combustion is extended along a direction in which the flame 22 is extended, i.e., the air for combustion is forced to flow in a state to be coincide with the extending direction of the flame and the air for combustion is excellently mixed with evaporated fuel to produce air-fuel mixture, this constitution prevents blow off of the flame 22, and enables stabilization of the flames 22 without the occurrence of turbulence of the flame.