[Problem] To provide a novel therapeutic agent for nocturnal pollakiuria. [Solution] A therapeutic agent for nocturnal pollakiuria which contains, as an active ingredient, (6S)-N-[4-({(2S,5R)-5-[(R)-hydroxy(phenyl)methyl]pyrrolidin-2-yl}methyl)phenyl]-4-oxo-4,6,7,8-tetrahydropyrrolo[1,2-a]pyrimidine-6-carboxamide.