An exemplary embodiment of the present application provides a method for preparing butadiene, the method comprising a process of performing an oxidative dehydrogenation reaction by introducing a reactant comprising butene, oxygen, nitrogen, and steam into a reactor which is filled with a catalyst, in which during a first start-up of the oxidative dehydrogenation reaction, the oxygen is introduced into the reactor before the butene, or the oxygen is introduced into the reactor simultaneously with the butene.