Provided is a silyl polymer-based antifouling coating composition that is capable of forming a coating film in which cracking is inhibited from occurring for a long period from the early stage of immersion in seawater and fresh water and enables to maintain excellent coating film consumption for a long term. The antifouling coating composition includes: a copolymer (A) containing a structural unit (a-1) derived from styrene or the like, a structural unit (a-2) derived from glycidyl (meth)acrylate, and optionally a structural unit (a-3) derived from another ethylenically unsaturated monomer; a polymer (B) containing a structural unit (b-1) derived from a monomer represented by the following Formula (b1): wherein X is a hydrogen atom or a carboxyl group; R1 is a hydrogen atom or a methyl group; R2 to R6, which may be the same as or different from each other, are C1-C6 straight or branched chain alkyl; and n is an integer of 0 or 1 or more; and an antifoulant.