Abstract: Process that is capable of synthesizing a metal-containing resin having a good antifouling property in a short period of time without having such problems associated with the synthesis as gelation. The process for producing a metal-containing resin by conducting a copolymerization reaction of a monomer mixture (A) comprising 1 to 50% by weight of a carboxyl group-containing polymerizable unsaturated monomer (a) and 50 to 99% by weight of other polymerizable unsaturated monomer (b) in an organic solvent in the presence of water and an oxide or hydroxide of a metal having a valency of at least 2, wherein the amount of water is 1 to 30 parts by weight based on 100 parts by weight of the monomer mixture (A), and the formation of a metal carboxylate bond occurs together with the copolymerization of the monomer mixture (A); and an antifouling coating composition containing, as an active constituent, a metal-containing resin obtained by the production process.