PURPOSE: To provide stable combustion from strong combustion to weak combustion by positioning the top of an outer flame cylinder higher than the upper end of an inner flame cylinder and providing a plurality of projections from the upper section of the outer flame cylinder towards the inner flame cylinder and providing a larger number of projections in the rear portion of a combustion cylinder than in the front portion.

CONSTITUTION: A combustion cylinder is formed with an inner flame cylinder 1 and outer flame cylinder 2. The outer flame cylinder top 7 which closes between the outer flame cylinder 2 and the top end of a heat resistant transparent cylinder 11 consisting of heat resistant glass is positioned at above the upper end of the inner flame cylinder 1, and a plurality of projections 9a which project towards the inner flame cylinder 1 are formed on the inner circumferential brim. The number of projections is larger in the front A than in the rear B of the combustion cylinder. When a wick 4 is lowered to provide weak combustion, the temperature of the atmosphere in the combustion cylinder becomes higher in the front A than in the rear B and the combustion quantity is larger due to the radiation heat from a reflection plate 7, but with this constitution a pressure loss is developed more in the section of a combustion chamber 3 between the inner flame cylinder and outer flame cylinder 1 and 2 which are the rear combustion cylinders so that the combustion quantity is suppressed, and the combustion chamber as a whole is in uniform red hot state. When the center of a plate 10 to expand flame is shifted rearwards, the same effect is obtained.