PURPOSE: To obtain the titled compound in high yield without using highly concentrated sulfuric acid, by reacting an N-unsubstituted acrylamide with an unsaturated ketone or aldehyde in the presence of a catalyst consisting of a cation exchange resin.

CONSTITUTION: An N-unsubstituted acrylamide shown by the formula I (R5 is H, or 1W5C alkyl) is reacted with an unsaturated ketone or aldehyde shown by the formula II (R1WR4 are H, alkyl, aralkyl, etc.) in the presence of a catalyst consisting of a cation exchange resin such as a strongly acidic cation exchange resin of sulfonic acid, etc., to give an N-substituted acrylamide shown by the formula III. A large amount of highly concentrated sulfuric acid is not required by the use of the catalyst, and so that neutralization treatment with an alkali after the reaction is not needed. When the reaction is usually carried out by a suspensoin using a stirring tank, the amount of the cation exchange resin is ≥3wt% based on the compound shown by the formula I , and the reaction temperature is preferably 40W150°C.