PURPOSE: To prevent adherence etc., of soot due to a flame transfer malfunction due to lifting, yellow flame and to prevent a decrease in burning performance by limiting a quantity of mixed gas to be supplied to a slit groove in contact with a flame transfer burner port of an outer burner port of a master burner cap and an inner burner port of a slave burner port.

CONSTITUTION: A protrusion 28 having a gradient part 27 for holding a predetermined gap substantially in parallel with a funnel-like oblique surface 23 provided on a master burner head 20 is provided on a rear surface of a master burner cap 14. A slit groove 30 communicating with the part 27 from an upper surface of the cap 14 is provided at the protrusion 28.