A periodontal bacterial growth inhibitor contains as an active ingredient a Macaranga tanarius extract extracted from Macaranga tanarius with an extraction solvent including at least an organic solvent. Alternatively, the periodontal bacterial growth inhibitor contains as an active ingredient at least one selected from nymphaeol-A, nymphaeol-B, and nymphaeol-C. The periodontal bacterial growth inhibitor is used by being blended to, for example, an oral hygiene product or a food and drink.
