Abstract: The present invention relates to an environmental friendly antifouling agent, and more particularly, to a novel Sargassum-derived antifouling agent which is harmless to environment, has antifouling activity against a broad spectrum of fouling organisms, can be extracted from nature, resulting in a relative reduction in production cost as compared with the existing antifouling substances, and can effectively prevent the pollution of marine environment caused by the use of toxic antifouling agents, such as TBT.