An electronic-component mounting package includes: an insulating wiring laminate including an upper surface; differential lines located on the wiring laminate; differential lines located on the upper surface and alongside the differential lines and having shorter line lengths than the differential lines; and a wall covering part of each of the differential lines and being in contact with the upper surface of the wiring laminate. The wall includes a protruding portion in plan view from above the upper surface, and portions of the differential lines, the portions being covered with the protruding portion, are longer than portions of the differential lines, the portions being covered with the protruding portion.