PURPOSE: To provide a stable combustion state by a method wherein a combustion air flowing from an air inlet port into an air flow passage is formed into a swirl flow by a swirler, injected into a tunnel of refractory block and then a recirculation area is formed within this tunnel to inject a raw fuel.

CONSTITUTION: Air for a combustion in a burner is flowed from an air inlet port 3 into an air flow passage 14, ascends within an air pipe 12, circulated by a swirler 17 and ascends in a tunnel 19. Plant raw fuel is flowed from an inlet seat 16b of an injection nozzle 16 and then injected from an injection hole 16a. A circulation flow 23 is formed by a swirl flow of air 22 for a combustion in a burner and then a recirculation area 25 is formed inside it. In turn, discharged gas 26 from a cell fuel is flowed from an inlet port 4 into an annular fuel flow passage 8, passes through a flowing port 9, flowed into an annular flow passage 13. After it ascends in it, the gas is injected from a slit 13a upwardly and ascends within the tunnel 19 along a tunnel wall 20a. The discharged gas 26 is mixed with air 22 and then a staying region 27 is formed near the tunnel wall 20a. With this arrangement, it is possible to get a stable combustion state.