PURPOSE: A moldable antifouling syntheric resin composition with durable antifouling property, that is composed of a synthetic resin, a specific agent controlling eluation and an antifouling agent of organotin.

CONSTITUTION: To a synthetic resin selected from the groups consisting of polyvinyl chloride, polyethylene, polypropylene, polyvinyl acetate, polystyrene and othres are added (B) 10W100wt% of one or more agents controlling eluation selected from monocarboxylate or dicarboxylate esters and (C) 1W10wt% of an organotin that is shown as the formula R3SnX or (R3Sn)2 Y (R is 1W8C alkyl, cycloalkyl, aryl, aralkyl; X is halogen, hydroxy, alkoxy, phenoxy, thioalkoxy, residue of monocarboxylic acid, residue of dimethylthiocarbamic acid; Y is O, S, residue of dicarbosylic acid) and dissolves in the agent controlling eluation in an amount of more than 0.1wt%.