Disclosed is a novel ingredient having an anti-obesity activity and a diabetes-ameliorating activity, which is obtained by focusing on a plant Albizzia julibrissin Durazz. Specifically disclosed are an anti-obesity agent and a diabetes-ameliorating agent, each of which comprises an extract from the flowers of Albizzia julibrissin Durazz., and from a preparation obtained by drying the flowers of Albizzia julibrissin Durazz. in particular.