PURPOSE:To keep the gas pressure in a hose low and make it possible to apply a gas fuel hose of a small diameter to a gas burner by providing a blower for sucking a gas fuel in the pipe passage which connects the connecting section of the gas fuel supply hose and the pipeline to which the gas burner is connected. CONSTITUTION:A pipeline 6 which is provided with a blower 5 for supplying the outdoor air as the combustion air is connected to a gas burner 2, and a pipeline 7 from the connecting section 15 of a gas fuel supply hose 14 and an indoor air suction passage 8 are connected on the suction side of the blower 5, and the gas fuel is completely burned in the combustion section 3, and at the same time a mixture gas of the combustion exhaust gas and surplus air is formed. Namely the gas fuel supply hose 14 is subject to a suction pressure by the blower 5. With this arrangement the gas fuel supply pressure is nearly the same as in the case in which only the gas fuel supply pressure works and still a sufficient quantity of the gas fuel is supplied even if the pressure loss per unit length of the hose is made larger so that it is possible to make the diameter of the gas fuel supply hose 14 small and an unexpected case of extinguishing fire or leaking the gas by stepping on the hose is prevented.