A method of producing a mixed manganese ferrite catalyst, and a method of preparing 1,3-butadiene using the mixed manganese ferrite catalyst. Specifically, a method of producing a mixed manganese ferrite catalyst through a coprecipitation method which is performed at a temperature of 10˜40° C., and a method of preparing 1,3-butadiene using the mixed manganese ferrite catalyst through an oxidative dehydrogenation reaction, in which a C4 mixture containing n-butene, n-butane and other impurities is directly used as reactants without performing additional n-butane separation process or n-butene extraction. 1,3-butadiene can be prepared directly using a C4 mixture including n-butane at a high concentration as a reactant through an oxidative hydrogenation reaction without performing an additional n-butane separation process, and 1,3-butadiene, having high activity, can be also obtained in high yield for a long period of time.