An antifouling coating composition comprising: a hydrolyzable resin having at least one kind of silicon-containing group selected from the groups represented by the following general formulas,, and and a metal-atom-containing group containing a divalent metal atom M; and a thermoplastic resin and a plasticizer wherein said thermoplastic resin is at least one kind selected from the group consisting of chlorinated paraffin, polyvinyl ether, rosin and a vinyl chloride-isobutylvinyl ether copolymer and wherein said plasticizer is at least one kind selected from the group consisting of a phthalate ester plasticizer and a phosphate ester plasticizer, wherein the total content of said thermoplastic resin and plasticizer is 3 to 100 parts by mass per 100 parts by mass of said hydrolyzable resin: wherein a and b each independently represent an integer of 2 to 5, m represents an integer of 0 to 50, and n represents an integer of 3 to 80; and R 1 to R 5 each independently represent an alkyl group, an alkoxy group, a phenyl group, a substituted phenyl group, a phenoxy group or a substituted phenoxy group; wherein c and d each independently represent an integer of 2 to 5, and p represents an integer of 0 to 50; R 6, R 7 and R 8 each independently represent an alkyl group, R a or R b; wherein R a represents wherein x represents an integer of 0 to 20; and R 23 to R 27 are the same or different and each represent an alkyl group, and R b represents wherein y represents an integer of 1 to 20; and R 28 and R 29 are the same or different and each represent an alkyl group; wherein e, f, g and h each independently represent an integer of 2 to 5, q and s each independently represent an integer of 0 to 50, and r represents an integer of 3 to 80; and R 9 to R 12 each independently represent an alkyl group, an alkoxy group, a phenyl group, a substituted phenyl group, a phenoxy group or a substituted phenoxy group; and wherein i, j, k and 1 each independently represent an integer of 2 to 5, t and u each independently represent an integer of 0 to 50, and v and w each independently represent an integer of 0 to 20; and R 13 to R 22 are the same or different and each represent an alkyl group. a hydrolyzable resin having at least one kind of silicon-containing group selected from the groups represented by the following general formulas,, and and a metal-atom-containing group containing a divalent metal atom M; and a thermoplastic resin and a plasticizer wherein said thermoplastic resin is at least one kind selected from the group consisting of chlorinated paraffin, polyvinyl ether, rosin and a vinyl chloride-isobutylvinyl ether copolymer and wherein said plasticizer is at least one kind selected from the group consisting of a phthalate ester plasticizer and a phosphate ester plasticizer, wherein the total content of said thermoplastic resin and plasticizer is 3 to 100 parts by mass per 100 parts by mass of said hydrolyzable resin: wherein a and b each independently represent an integer of 2 to 5, m represents an integer of 0 to 50, and n represents an integer of 3 to 80; and R 1 to R 5 each independently represent an alkyl group, an alkoxy group, a phenyl group, a substituted phenyl group, a phenoxy group or a substituted phenoxy group; wherein c and d each independently represent an integer of 2 to 5, and p represents an integer of 0 to 50; R 6, R 7 and R 8 each independently represent an alkyl group, R a or R b; wherein R a represents wherein x represents an integer of 0 to 20; and R 23 to R 27 are the same or different and each represent an alkyl group, and R b represents wherein y represents an integer of 1 to 20; and R 28 and R 29 are the same or different and each represent an alkyl group; wherein e, f, g and h each independently represent an integer of 2 to 5, q and s each independently represent an integer of 0 to 50, and r represents an integer of 3 to 80; and R 9 to R 12 each independently represent an alkyl group, an alkoxy group, a phenyl group, a substituted phenyl group, a phenoxy group or a substituted phenoxy group; and wherein i, j, k and 1 each independently represent an integer of 2 to 5, t and u each independently represent an integer of 0 to 50, and v and w each independently represent an integer of 0 to 20; and R 13 to R 22 are the same or different and each represent an alkyl group.