A gas furnace includes: a combustion part in which a fuel gas is burnt to generate a combustion gas; a heat exchanger having a gas flow path through which the combustion gas flows; a blower configured to blow air around the heat exchanger; and an inducer configured to discharge the combustion gas from the heat exchanger, wherein the heat exchanger includes: at least one single path in which a single gas flow path is formed; a single-multiple return bend configured to communicate with the single path and convert a flow direction of the combustion gas; and at least one multiple path having a plurality of paths that communicate with the single-multiple return bend and form multiple gas flow paths.