Abstract: A gas burner having flame openings adapted for discharging a mixture of gaseous fuel and primary combustion air supplied from an electric fan, and secondary air supply passages adapted for supplying secondary combustion air from the electric fan into a combustion space adjacent the flame openings. The gas burner is characterized by opposed combustion face forming wall members extending from the sides of the flame openings, in the mixed gas discharge direction and at the same time diverging outwardly with the secondary combustion air outlet openings formed continuously or intermittently along lines extended from both ends of the flame openings on the faces of the wall members towards the direction of mixed gas flow.