Abstract: A process for the production of antimony-containing metal oxide catalysts, comprising preparing a slurry containing as essential components an antimony component, a polyvalent metal compound, and silica sol, heating and drying the slurry to form a solid product, and then calcining the solid product, wherein the antimony component is a mixture of (A) at least one of antimonic acid, polyantimonic acid and the salts thereof and (B) antimony trioxide, and is prepared by mixing (A) and (B) in such a manner that the antimony provided by the (B) constitutes from 0.1 to 70 atomic % of the total amount of antimony and further in an aqueous slurry state. These antimony-containing metal oxide catalysts have superior activity and physical properties, and further reproducibility in the preparation thereof. Thus they are useful for production of aldehydes and acids through oxidation, nitriles through ammoxidation, and dienes, unsaturated aldehydes and unsaturated acids through oxidative dehydrogenation.