The electronic-component-mounting board according to the present invention includes: a high-heat-dissipation substrate including a metal plate and a circuit pattern formed on a upper surface of the metal plate; an electronic component which is mounted on the high-heat-dissipation substrate and is electrically connected to the circuit pattern; and one external connection terminal which is disposed on the high-heat-dissipation substrate and provides electrical connection between the electronic-component-mounting board and an external device. The external-connection terminal is formed of a material having a thermal conductivity less than that of the metal plate and has at least one external electrode to which a lead wire is soldered. Therefore, the lead wire can be connected by soldering even on the high-heat-dissipation substrate. Accordingly, the reliability of the electrical connection is improved, and reduction in size and thickness of the electronic-component-mounting board can be achieved. In addition, the cost of the electronic-component-mounting board can be reduced.