In a method for forming a three-dimensional interconnection, a contact plug is formed within a through hole provided in a substrate and an upper wire formed on an upper side of the substrate and a lower wire formed on a lower side are electrically connected to one another by the contact plug. A coating film is formed on an upper surface of the substrate and inner surface of the through hole by applying a metal film-forming composition containing at least one salt of and a particle of a metal to the substrate provided with the through hole. A metal film is formed by heating the coating film, and plated by filling up the through hole by depositing a conductor on the metal film by a plating process using the metal film as a seed layer. An excess conductor deposited in the plating is removed by a chemical mechanical polishing process.