A metal film-forming method is capable of forming a metal film on a surface of a base metal film, formed on a surface of a substrate, with sufficient adhesion to the base metal film even when a natural oxide film is formed on the surface of the base metal film. The metal film-forming method includes: preparing a substrate having a base metal film formed on a surface; and carrying out electroplating of the substrate using the base metal film as a cathode and another metal as an anode while immersing the substrate in a solution containing a metal complex and a reducing material, both dissolved in a solvent, to form a metal film, deriving from a metal contained in the metal complex, on the surface of the base metal film.