The present invention provides a ceramidase activity inhibitor which inhibits ceramidase activity, specifically neutral/alkaline ceramidase activity, characterized in that the inhibitor comprises, as an active ingredient, a processed product derived from at least one plant selected from the group consisting of plants belonging to Ginkgoaceae, plants belonging to Cucurbitaceae, plants belonging to Rutaceae, plants belonging to Laminariaceae, plants belonging to Myrtaceae and plants belonging to Compositae, and a medicament, a quasi-drug, cosmetics and a food, each comprising the inhibitor.