A mount substrate includes: an insulation substrate containing resin and glass; connection conductors formed on a surface of the insulation substrate; a first white resist layer that covers the connection conductors; and a second white resist layer that covers the first white resist. Each of the connection conductors includes a copper foil and a plating layer partly formed on the copper foil. The plating layer is formed of metal having oxidation-resistant and corrosion-resistant characteristics higher than those of copper. The first white resist layer is formed with first openings that respectively expose the plating layers of the connection conductors. The second white resist layer covers a periphery of each plating layer of the connection conductors in planar view.