To produce an ester useful as industrial chemicals, medicaments, perfume, dye, an organically synthetic intermediate or the like in a good yield in one step by reacting a specific carbonyl compound with a specific oxime ester or a specific enol ester in the presence of an alkoxide.

By reacting 1 mol carbonyl compound of formula I (wherein, R1 and R2 are each H or an organic group) with preferably 0.8-5 mol oxime ester compound of formula II (wherein, R3-R5 are each a nonreactive atom or the like) or enol ester compound of formula III(wherein, R6-R8 are each H, a 1-5C alkyl or the like) in the presence of an alkoxide of a group III element (e.g. scandium isopropoxide or the like) preferably at 10-60°C for 10 min to 48 h., an ester of formula IV is obtained. The consumed amount of the alkoxide of a group III element is preferably 1.5-3 equivalent times the amount of the compound of formula I.