PURPOSE:To obtain good combustion state by a structure wherein bent parts are provided respectively at a part of a primary air passage and of a secondary air passage and yet a fuel pipe is arranged upstream side of the bent part of the primary air passage. CONSTITUTION:The upstream side and downstream side of the secondary air passage 20 equipped with the bent part 20a are communicated respectively to a secondary air port 18b and a secondary air blast nozzle 24 provided at the back 1a of a burner main body 1. The tertiary air passage 21 communicates to a tertiary air port 18c and a tertiary air blast nozzle 25 provided at the back 1a of the burner main body 1. The tip part of the fuel pipe 22 connected upstream side the bent part 19a of the primary air passage 19 is inserted to the central part within the primary air passage 19 and at the same time arranged a pair of its blast nozzles 22a normal to the direction of primary air flow or to the inner wall of the primary passage 19. Due to the structure as described above, good combustion state can be obtained.