Abstract: An antifouling coating composition having excellent antifouling performance and coating film performances comprising a vehicle, an antifouling agent and optionally other additives characterized by containing, as at least a part of said vehicle, a polymer constituted of at least one monomer represented by the following general formula: ##STR1## wherein R is hydrogen or methyl group and R' is hydrogen or alkyl group having 1-12 carbon atoms, or of said at least one monomer and other vinyl monomer copolymerizable therewith, having a glass transition temperature of -30.degree. C. to 0.degree. C. and having a weight average molecular weight falling in the range of 20,000-200,000.