The antifouling coating composition of the present invention includes (A) at least one hydrolyzable copolymer selected from the group consisting of specific metal salt bond-containing copolymers and a silyl ester copolymer, (b1) copper and/or an inorganic copper compound and (C) zinc oxide, wherein (1) the content of the antifouling agent (B) is in the range of 100 to 400 parts by weight and the content of the zinc oxide (C) is in the range of 50 to 350 parts by weight, each content being based on 100 parts by weight of the hydrolyzable copolymer (A), and (2) the weight ratio of the zinc oxide (C) to the copper and/or the inorganic copper compound (b1) (zinc oxide (c1)/(copper and/or inorganic copper compound (b1))) is in the range of 0.6 to 1.2. The present invention provides a coating material, particularly a novel antifouling coating composition which is a hydrolyzable antifouling coating composition, and forms an antifouling coating film which is excellent particularly in antibacterial action and renewal of coating film with a good balance between them and can effectively prevent adhesion of marine organisms for a long period of time when it is applied to a surface of a substrate of a ship's s hull or the like and then cured.
