The invention relates to a continuous method for producing hydroxycarboxylic acid amides, according to which at least one hydroxycarboxylic acid of formula (I) HO—R3—COOH  (I) wherein R3 is an optionally substituted aliphatic hydrocarbon group comprising between 1 and 100 carbon atoms, is reacted with at least one amine of formula (II) HNR1R2  (II) wherein R1 and R2 are independently hydrogen or a carbon group comprising between 1 and 100 C atoms, to form an ammonium salt, and said ammonium salt is then reacted to form a hydroxycarboxylic acid amide, under microwave irradiation in a reaction pipe, the longitudinal axis of the pipe being oriented in the direction of propagation of the microwaves of a monomode microwave applicator.