The present invention, which minimizes air-film unevenness while also minimizing flashback, is provided with a pilot burner and a plurality of main burners (36) provided in a circumferential direction around the pilot burner, radially outwards with respect thereto. Each main burner has the following: a main nozzle (36a) positioned inside a main-burner cylinder (36A); an extension tube (36B) that extends downstream from said main-burner cylinder, has a circular entrance (36Ba) to which that main-burner cylinder leads, and has a downstream exit (36Bb) formed from two radial edges (36Bc) and two circumferential edges (36Bd) that join the ends of the radial edges in the circumferential direction; an air passage (36E) provided outside that main-burner cylinder; and an inside connecting hole (H1) that connects that air passage to the interior of the entrance side of that extension tube at a point that corresponds to the radially inner circumferential edge thereof.