PROBLEM TO BE SOLVED: To provide a fat accumulation inhibitor serving as an antiobesity agent.SOLUTION: A fat accumulation inhibitor contains acid mucopolysaccharides represented by the following formula (1) and produced by marine bacteria or a physiologically acceptable salt or a derivative thereof as an active ingredient. The fat accumulation inhibitor is preferably a skin external preparation or drink and food for cosmetic. In the formula (1), GlcNAcp represents a pyranose-type N-acetylglucosamine residue, GlcUAp represents a pyranose-type glucuronic acid residue, Glu represents a glutamic acid, D represents a D form, L represents an L form, n represents the number of repetition indicting that the average molecular weight is 1,000,000 to 1,500,000 on the basis of a pullulan standard in measurement by gel filtration chromatography.
