Oxide catalyst, method of producing the oxide catalyst, a method for producing an unsaturated acid and a method for producing an unsaturated nitrile

Provided a method of producing an oxide catalyst, which method of producing the oxide catalyst used for the catalytic gas phase oxidation of propane and the like reactions, the method comprising: (I) to give a predetermined ratio of atoms containing Mo, V, Nb , Sb or Te step of modulating each compound solution, (II) modulation was dried to obtain a dry powder process, and (III) a step of calcining the dried powder, (III) firing step comprises: drying by the solid powder and the W-containing compound to coexist and calcined to obtain a calcined powder or a pre-stage calcined powder; and baking or coexist with the solid obtained by calcining the dried powder of pre-stage calcined powder, thereby a step to obtain calcined powder, the solid predetermined condition is satisfied, the oxide catalyst comprising a catalyst component having a predetermined composition.