Abstract: A coating agent for forming an oxide film; a method for producing an oxide film; and a method for producing a metal-plated structure, where the stability of the coating agent can be enhanced, and an oxide film which can be plated and has high adhesion to a substrate can be easily formed. The coating agent for forming an oxide film is a liquid coating agent, essentially contains titanium atoms, and optionally contains silicon atoms and copper atoms, wherein the ratio of the sum of the titanium atoms and copper atoms to the silicon atoms is 1:0-3:2. The method for producing an oxide film includes applying the coating agent to a substrate and heating to form an oxide film. The method for producing a metal-plated structure includes: a metal-film-forming step for forming a metal film on the oxide film; and a baking step for baking the metal film.