Abstract: The present invention addresses the problem of a providing NMN having high purity and a low impurity content. The present invention is a high-purity ?-nicotinamide mononucleotide (NMN) which has a purity of 99.0 mass % or higher and in which the amounts of C11H15NO9P, C10H16N5O10P2, C9H15N3O8P, C9H15N3O7P, C9H16N4O8P, C10H15N5O7P, and C21H27N6O15P2 contained as impurities are equal to or less than a detection limit.