PURPOSE: To widely adjust the heating power of a burner, by connecting an air box to a pressurization air, constituting each orifice with a cylindrical hole, and at the same time providing a mechanical obstacle for crossing the central region of the exit of the orifice.

CONSTITUTION: A cylindrical side surface wall 2 and a wall 3 of an air box 1 in a shape being determined by two flat walls 3 and 4 in a side direction become a porous wall with an orifice 5 being arranged with a number of small mutual intervals, and the inner surface of the orifice is a cylindrical surface. The other wall 4 has a duct 6 so that the duct 6 penetrates the wall 4, and the duct connects the air box to an external pressurization air source such as a fan. A mechanical obstacle 16 is provided on the extension line of the axial line of each needle 11. The obstacle 16 changes the direction of a gas jet exiting the needle and causes turbulence in a certain form, thus securing enabling the gas jet to be mixed with pressurization air that surrounds the gas jet.