A method for producing a thin-film battery includes a film-formation step of forming a film of a positive-electrode material to form a positive-electrode active material film and an annealing step of annealing the positive-electrode active material film. After the annealing step, a lithium-ion introduction step of introducing lithium ions into the positive-electrode active material film. After the introduction of the lithium ions, a reverse-sputtering step of edging the positive-electrode active material film by reverse sputtering.