Process for preparing an amine by reacting an aldehyde and/or ketone with hydrogen and a nitrogen compound selected from the group consisting of primary and secondary amines in the presence of a heterogeneous catalyst, wherein the reaction is carried out using a suspended catalyst as heterogeneous catalyst and is carried out in the semibatch mode in which the nitrogen compound as one reactant is placed in the reaction vessel and the aldehyde and/or the ketone as the other reactant is added during the course of the reaction and the aldehyde and/or the ketone is added in portions or continuously to the reaction mixture during the course of the reaction as a function of the achieved conversion of the nitrogen compound until a conversion of the nitrogen compound of at least 95% results, and all or part of the catalyst remains in the reaction vessel after the reaction batch and is reused for the next reaction batch.