To attempt to shorten a flame while stably holding ignition and to realize the reductions in size and cost of a furnace by giving a turning force to the air passing an outside air passage by a blade radially provided along the circumferential direction of a secondary air passage to generate a strong circulating flow.

Combustion air is introduced from an air register to a flame stabilizer via an annular air passage 8, and branched to a second air passage 16 having an outer blade 6 and an inner second air passage 10 of an inner cylinder 9. The air passing the passage 16 becomes a circular flow by the blade 6, is agitated and mixed with fuel to be atomized by an atomizer, a strong circulating flow B flowing toward the center is generated, a low speed area ignitable is formed at the periphery of the atomizer, the vortex of stable air is formed, and flame stabilized. The air M passed through the passage 10 is formed with a vortex by a diffuser 11, and the ignition of fuel atomized from the atomizer can be accelerated and stabilized.