According to one embodiment, an interposer substrate for switching wiring lines, includes a substrate body having through holes penetrating from a first main surface thereof to a second main surface, through-conductive portions provided respectively in the through holes, grouped into first groups and second groups different from the first groups, first wiring lines each provided on the first main surface and for a respective one of the first groups, second wiring lines each provided on the second main surface and for a respective one of the second groups, first terminals provided on the first main surface and connected respectively to the first wiring lines, and second terminals provided on the second main surface and connected respectively to the second wiring lines.