PURPOSE: To improve the in-furnace temp. distribution of a gas combustion type glass fusing furnace.

CONSTITUTION: This glass fusing furnace is constituted to heat a lower fusing vessel by the direct heat from the flames of an external mixing type gas burner 2 installed through the side wall 3 of the furnace and the reflected heat from a ceiling. Auxiliary gas nozzles 7 are branched from the main gas nozzle 6 of this gas burner 2. These nozzles are inserted into a main nozzle insertion hole 8 and auxiliary nozzle insertion hoes 9 respectively bored at the furnace wall 3. Auxiliary flames of the flame length shorter than the main flames ejected out of the main gas nozzle 6 are ejected out of the auxiliary nozzles 7. As a result, distances to the extent to prevent mingling of the flames with each other are assured between the main gas nozzle 6 and the auxiliary nozzles 7 and, therefore, the auxiliary flames are independently burned without being affected by the main flames, by which the max. radiation parts of the auxiliary flames are brought alongside the low-temp. parts at the root of the main flames. The approximation of the in-furnace temp. distribution to an ideal pattern is thus made possible without shortening the length of the main flames.