A gas furnace according to an embodiment of the present disclosure includes: a mixer for mixing air and a fuel gas, which are introduced through an intake pipe and a manifold, respectively, to form a mixture; a mixing pipe through which the mixture, having passed through the mixer, flows; a burner assembly for producing a combustion gas by burning the mixture having passed through the mixing pipe; a heat exchanger through which the combustion gas flows; an exhaust pipe through which an exhaust gas, as the combustion gas having passed through the heat exchanger, is discharged outside of the gas furnace; and an inducer for inducing a flow of a fluid through the intake pipe, the mixer, the mixing pipe, the burner assembly, the heat exchanger, and the exhaust pipe. In this case, the mixer has a front end connected to the intake pipe, a rear end connected to the mixing pipe, and a side surface connected to the manifold.