Methods of producing a safe and hygienic method for industrially and efficiently producing a perovskite-type composite oxide are provided that can maintain the catalytic activity of a noble metal at a high level. Methods include preparing a precursor of the perovskite-type composite oxide by mixing organometal salts of elementary components of the perovskite-type composite oxide and heat treating the precursor. The precursor may be prepared by mixing all elementary components constituting the perovskite-type composite oxide, or by mixing one or more organometal salts of part of the elementary components with the other elementary components prepared as alkoxides, a coprecipitate of salts, or a citrate complex of the respective elements.