Provided are an antifouling coating composition containing a hydrolyzable resin having a specific silicon-containing group and a triorganosilyl oxycarbonyl group, an antifouling film, a composite film and an in-water structure such as a ship using the same. The hydrolyzable resin may further have a specific metal-atom-containing group containing a divalent metal atom. By the antifouling coating composition, it is possible to form a coating film having excellent crack resistance, while exerting an excellent antifouling property for a long period of time even when no or a small amount of antifouling agent is contained.