An antifouling coating composition which makes it possible to control the dissolution rate of a coating film and which can exert antifouling properties for a long period of time. An antifouling coating composition comprising an antifouling resin (A) obtained by reacting a base resin including, in one molecule, a carboxyl group and a group having a polyalkylene glycol structure with an oxide or a hydroxide of a divalent or more metallic atom in the presence of water in an amount of 1 to 30% by weight of the solid content of the base resin, and an antifouling agent (B).