According to the present disclosure, a resin product is brought in contact with a treatment liquid containing an antiviral compound (A) of a quaternary ammonium halide having a molecular weight of not greater than 1500 and, in this state, heat-treated under a normal pressure or under an increased pressure, whereby the antiviral compound (A) is immobilized on at least a surface of the resin product. Thus, an excellent antiviral finished product having water resistance and laundry durability is provided.
