A method of preparing butadiene and a device for preparing the same. The method includes passing reaction raw materials containing butene, oxygen, steam, and a diluent gas through an oxidative dehydrogenation reactor, and oxidative dehydrogenation is performed therein to produce a reaction product separating water from the reaction product condensing hydrocarbons to produce a crude hydrocarbon mixture; and separating butadiene from the crude hydrocarbon mixture, where a gas containing n-butane remaining after the butadiene is separated is fed into the oxidative dehydrogenation reactor, and butane is used as a diluent gas. Because butane is used as a diluent gas, a C4 mixture and gas products may be easily separated through cooling and condensation processes. Thus, the method may increase productivity while reducing energy consumption and raw material costs, thereby improving economic efficiency.