PURPOSE: To reduce the manufacturing cost and enable stable use for a long period of time by providing a plurality of slits for relaxing thermal stress at the end section of a cone for burner of approximately cylindrical shape made of ceramic.

CONSTITUTION: Fuel oil sprayed out of a burner nozzle 9 is mixed with combustion air from a wind box 3 and ignited to form a stable flame in a cone 8 for burner. Since the cone 8 is made of ceramic having high thermal resistance and corrosion resistance, the cone 8 is not affected by corrosive substances contained in the fuel. Since slits 11 are formed on the end section 10 which directly contacts the flame and hence the generation of thermal stress can be reduced, cracks are prevented from occurring in said section. Further, the cone made of ceramic can by manufactured by simply forming a cone and burning it, resulting thereby at a reduced manufacturing cost.