PURPOSE: To enable uniform ignition to be performed in a width direction of a machine by a method wherein a set of fuel headers are arranged with being crossed at a right angle in the advancing direction of a pallet, a first air header is arranged between the fuel headers, a second air header is arranged outside the fuel headers and then air from the air headers is injected against the injected fuel.

CONSTITUTION: A set of fuel headers 11 and 12 are arranged in the advancing direction of a pallet by being crossed at a right angle, a first air header 20 is arranged between the fuel headers 11 and 12, and second air headers 21 and 22 are arranged outside the fuel headers. When equal amount of air for combustion is fed from the first air header 20 and second air headers 21 and 22, fuel gas from fuel injection ports 11a and 12 a advances directly toward a surface of raw material to get two parallel flames. By varying a feeding rate, a shape of each of the flames can be controlled. In this case, since combustion air strikes against each other from both sides with fuel gas left therebetween, a rapid combustion can be performed and the unburnt component can be completely burnt. In this way, an ignition which is uniform in a lateral direction can be carried out and an efficient countermeasure can be taken for a variation in nature of raw material and variation various dimensions of production by varying the shape of and the height of each of the flames in the burner.