To provide a gas-air mixing device for a gas burner capable of easily changing a combustion performance corresponding to the type of gas not only through adjustment of an amount of air but also by a throat length and a shape of throat portion, which are important for a mixing of gas and air and a controlling of combustion state without performing any adjustment of an amount of air and without increasing the number of prior art component parts.

A technical assumption in this invention consists in a gas-air mixing device for a gas burner comprised of a burner part for igniting mixture of gas and air; adjusting means for inputting air and adjusting an air flowing amount; and a gas nozzle connected to a gas pipe to inject gas, wherein the adjusting means is constituted by an adjusting component part having an inner diameter hole for passing an amount of air corresponding to the type of gas.