The optical thin film is provided on a substrate and includes, in order, from the substrate side, an interlayer, a silver-containing metal layer, and a dielectric layer, in which an anchor region including an oxide of an anchor metal is provided in an interface region of the silver-containing metal layer on a side close to the interlayer, a cap region including an oxide of the anchor metal is provided in an interface region of the silver-containing metal layer on a side close to the dielectric layer, a film thickness of the silver-containing metal layer is 6 nm or less, the silver-containing metal layer contains a high standard electrode potential metal, and a peak position of a concentration distribution of the high standard electrode potential metal in a film thickness direction of the silver-containing metal layer is positioned closer to the interlayer than a peak position of a silver concentration distribution.