The present invention relates to a method for purifying N-substituted maleimide. More particularly, the present invention adopts an evaporation apparatus, which can previously remove impurities having higher boiling points than the N-substituted maleimide after removing an organic solvent from an N-substituted maleimide resulting solution, thereby achieving effects of minimizing the pressure loss and polymerization loss, and obtaining high-purity N-substituted maleimide.