[Problem to be Solved] To provide a method of well filling copper in a non-through hole on a conductivity-rendered substrate by using a copper plating bath containing fewer additives.[Means for Solving the Problem] A method of filling copper in a non-through hole on a substrate that has been treated to render it conductive, which comprises plating said substrate in an acidic copper plating bath comprising a water-soluble copper salt, sulfuric acid and a filling additive that is a polymer having the activities of both of a brightener and a leveler.