PURPOSE: To prepare the titled comound useful as a perfumery, pharmaceutical, etc. or their raw material, easily in high yield, by the dehydrogenative oxidation of an unsaturated alcohol in an atmosphere of an oxygen-donative substance such as air, in the presence of an oxovanadium (IV) catalyst.

CONSTITUTION: The unsaturated carbonyl compound of formula II (e.g. citral) is prepared by the dehydrogenative oxidation of the unsaturated alcohol of formula I (R1WR4 are H, alkyl, alkenyl or aryl) (e.g. geraniol) with an oxygen- donative substance such as oxygen gas, a mixture of oxygen and inert gas or air, etc. in the presence of an oxovanadium (IV) catalyst such as vanadium acetylacetonate. The reaction is preferably carried out by adding an antioxidant to the reaction system and diluting the reaction system with a solvent to suppress the side reactions.