A substrate joined body including: a first substrate; a second substrate; an organic film that comprises silicon and carbon and joins the first substrate and the second substrate; and a protective film that comprises an inorganic element and is formed over the organic film from at least a part of the surface of the first substrate and at least a part of the surface of the second substrate, wherein the protective film comprises a region in which the ratio of carbon to silicon based on atomic percentage is from 0.0 to 5.0 in a region within 50 nm in a thickness direction from a surface of the organic film on the protective film side, when the surface is measured by X-ray photoelectron spectroscopy.