The invention relates to a surface treatment method and a surface treatment device. The surface treatment method includes: roughening a surface region of a substrate corresponding to a through hole provided to a masking plate by supplying a solvent to a solid electrolyte film from a second surface of a masking plate through the through hole, in a state where: a first surface of the solid electrolyte film is arranged directly on the surface of the substrate; and a first surface of the masking plate is arranged directly on a second surface of the solid electrolyte film, wherein the supplied solvent penetrates the solid electrolyte film, and dissolves the surface of the substrate.