An antifouling coating composition comprising a hydrolyzable copolymer comprising a structural unit derived from triisopropylsilyl methacrylate (i), a structural unit derived from 2-methoxyethyl (meth)acrylate (ii), and a structural unit derived from a polymerizable monomer (iii) having a polymerizable double bond, with the proviso that triisopropylsilyl methacrylate and 2-methoxyethyl (meth)acrylate are excluded, cuprous oxide having an average particle size as measured according to the method disclosed in the description of 4.5 to 50 μm, and a rosin and/or a monocarboxylic acid compound, wherein the rosin is selected from gum rosin, wood rosin, tall oil rosin, hydrogenated rosins and disproportionated rosins, the monocarboxylic acid compound is selected from aliphatic or alicyclic monocarboxylic acids, the ratio (WA/WC) of the content of the hydrolyzable copolymer to the content of the rosin and/or the monocarboxylic acid compound is 95/5 to 40/60 by mass, the hydrolyzable copolymer is present in an amount of 7 to 30 mass% of the content of solids of the antifouling coating composition taken as 100 mass%, and the antifouling coating composition does not comprise medetomidine. a hydrolyzable copolymer comprising a structural unit derived from triisopropylsilyl methacrylate (i), a structural unit derived from 2-methoxyethyl (meth)acrylate (ii), and a structural unit derived from a polymerizable monomer (iii) having a polymerizable double bond, with the proviso that triisopropylsilyl methacrylate and 2-methoxyethyl (meth)acrylate are excluded, a structural unit derived from triisopropylsilyl methacrylate (i), a structural unit derived from 2-methoxyethyl (meth)acrylate (ii), and a structural unit derived from a polymerizable monomer (iii) having a polymerizable double bond, with the proviso that triisopropylsilyl methacrylate and 2-methoxyethyl (meth)acrylate are excluded, cuprous oxide having an average particle size as measured according to the method disclosed in the description of 4.5 to 50 μm, and a rosin and/or a monocarboxylic acid compound, wherein the rosin is selected from gum rosin, wood rosin, tall oil rosin, hydrogenated rosins and disproportionated rosins, the monocarboxylic acid compound is selected from aliphatic or alicyclic monocarboxylic acids, the ratio (WA/WC) of the content of the hydrolyzable copolymer to the content of the rosin and/or the monocarboxylic acid compound is 95/5 to 40/60 by mass, the hydrolyzable copolymer is present in an amount of 7 to 30 mass% of the content of solids of the antifouling coating composition taken as 100 mass%, and the antifouling coating composition does not comprise medetomidine. the rosin is selected from gum rosin, wood rosin, tall oil rosin, hydrogenated rosins and disproportionated rosins, the monocarboxylic acid compound is selected from aliphatic or alicyclic monocarboxylic acids, the ratio (WA/WC) of the content of the hydrolyzable copolymer to the content of the rosin and/or the monocarboxylic acid compound is 95/5 to 40/60 by mass, the hydrolyzable copolymer is present in an amount of 7 to 30 mass% of the content of solids of the antifouling coating composition taken as 100 mass%, and the antifouling coating composition does not comprise medetomidine.