To simply obtain the subject compound, in a high yield, that is useful as a starting substance for analgesic disease-therapeutic agent by carrying out the Michael addition reaction in an aqueous solution with no use of any organic solvent from the start of the reactions to the isolation of the addition reaction product.

A ketone represented by formula I (R1 and R2 are H, a halogen, an alkyl) with particle sizes of 20-100μm, an amine of the formula: R3-N (R3 is an alkyl of 4 or more carbon atoms) are allowed to react with each other under agitation rate of 250-350rpm, as a cationic quaternary ammonium surfactant of formula II (R4 is a straight-chain alkyl of 7 or more carbon atoms; R5 is a straight-chain alkyl of 1-3 carbon atoms; X is a halogen) (for example, butyltrimethylammonium bromide is used in an amount 0.025 mole per mole of the compound of formula I, in the case that the weight ratio of the compound of formula I to water is 1/10, to produce the objective ketone bearing a substituted amino group in the β-position.