[Problem] Fucoxanthin extracted from wakame seaweed (Undaria pinnatifida) is effective as an anti-obesity active agent. However, fucoxanthin is contained in mature (adult) brown algae in a small amount, and accordingly, it takes a long time and high cost to obtain fcoxanthin in an amount sufficient for practical use. Further, an anti-obesity active agent showing a stronger effect has been desired. It is, therefore, an object of the present invention to specify a carotenoid exhibiting anti-obesity activity stronger than that of fucoxanthin and to provide an anti-obesity active agent and an anti-obesity method which use the caritenoid.[Means to Solve the Problem] Intensive and extensive studies have been made as to what carotenoid has an anti-obesity activity stronger than that of fucoxanthin and what material should be used in order to economically obtain such a carotenoid. As a result, the answer has been found that the carotenoid is fucoxanthinol. “Sea squirt (ascidian)” is a generic name of marine animals which belong to class Ascidiacea, subphylum Urochordata (Tunicata), phylum Chordata and which live nationwide. As described above, sea squirt (ascidian) is abundantly found as resources. In the present invention, fucoxanthinol is extracted particularly from internal organs and hard skins of sea squirt (ascidian), and it has been revealed that fucoxanthinol exhibits strong anti-obesity activity.