The present invention relates to a method of preparing a catalyst for oxidative dehydrogenation. More particularly, the method of preparing a catalyst for oxidative dehydrogenation includes a first step of preparing an aqueous iron-metal precursor solution by dissolving a trivalent cation iron (Fe) precursor and a divalent cation metal (A) precursor in distilled water; a second step of obtaining a slurry of an iron-metal oxide by reacting the aqueous iron-metal precursor solution with ammonia water in a coprecipitation bath to form an iron-metal oxide (step b) and then filtering the iron-metal oxide; and a third step of heating the iron-metal oxide slurry.In accordance with the present invention, a metal oxide catalyst, as a catalyst for oxidative dehydrogenation, having a high spinel phase structure proportion may be economically prepared by a simple process.