A polymer composite according to the present invention is characterized by comprising: a polymer containing a structural unit derived from an unsaturated monomer; and metal components dispersed in a matrix composed of the polymer, wherein the metal components are at least one selected from a zirconium component, an yttrium component, a cerium component, and a neodymium component. The metal components are preferably metal oxides or metal ions. The polymer composite according to the present invention can be produced by a method which sequentially comprises: a mixing step for mixing sol containing water and a metal oxide or an aqueous solution containing metal ions, an unsaturated monomer, and a polymerization initiator; and a polymerization step for polymerizing the unsaturated monomer.