PURPOSE: To attain a continuous stable flame from a flame hole corresponding to a recessed part and improve ignition performance by a method wherein the flame hole for removing pressure by communicating the mixing chamber with the outside is provided at a part corresponding to the recessed part of a burner cap.

CONSTITUTION: A part corresponding to a recessed part 62 of a burner cap 7 is provided with a flame hole 14a for removing pressure communicating with a mixing chamber 6A. Due to this arrangement, a part of the mixture gas becomes a flame and escapes out of a flame hole 14a to outside. Therefore, it is possible to get such a flame as one having no influence of pressure, and no disturbance, at the flame hole corresponding to a recessed part 62, i.e. a flame hole between an elongated projection 7B and a projecting tooth 74 and a flame hole between the projecting teeth 74 and 75. Then, the flame becomes a stable state having no lift or back-fire, a heating condition in respect to a thermocouple 10 is improved, an erroneous operation of the thermocouple 10 is eliminated and thus a desired normal function can be assured. Thus, in case that an ignition electrode is arranged in the recessed part 62, igniting characteristic can be improved.