Abstract: A staged air burner having a swirl chamber for providing a swirl flow path for primary combustion air, a tangential duct system for providing a tangential flow path for primary combustion air flowing toward the swirl flow path, and a converging passage structure for providing a converging flow path for secondary air which flows along the converging flow path inwardly toward an axis of the swirl chamber downstream of the latter. At least two fuel supply systems are respectively situated at two of the above flow paths for supplying combustible fuel thereto so that it is possible to fire fuel simultaneously at least at two of the flow paths.