To optimally set an interval between the opening rim of a central injection port and the opening rims of peripheral injection ports, as well as the ratio of a gas fuel injection amount between the central injection port and the plurality of peripheral injection ports.

A combustion device for a heating furnace is provided with a fuel injection unit 7, equipped with a central injection port 72a and a plurality of peripheral injection ports 72b arranged around the central injection port 72a, and an oxygen containing gas- supplying unit for supplying oxygen containing gas for combustion. In such a combustion device, the gas fuel injection direction of the plurality of peripheral injection ports 72b are devised, so as to be in parallel or substantially parallel to the gas fuel injecting direction of the central injection port 72a and an interval between the opening rim of the central injection port 72a, and the opening rim of the peripheral injection ports 72b is specified so as to be 0.5 times or larger than the diameter of the peripheral injection port 72b or specified so as to be 1.5 times or smaller than a value obtained by adding the diameter of the central injection 72a to the diameter of the peripheral injection port 72b, while 50-75% of the total injecting amount of gas fuel from the fuel injection unit 7 is made to be injected from the central injection port 72a and the remaining amount of the total injecting amount is devised to be injected from the plurality of peripheral injection ports 72b.