A multi-layer substrate includes a plurality of substrate main bodies, a plurality of layers which are alternately layered with the main bodies, a signal via hole which is connected with a signal line and includes a signal column which passes through at least one substrate main body; and a sub via hole which includes a sub column which surrounds the signal column, and a pair of sub pads which extend from end parts of the sub column to be formed to the layers, the layers which are formed with the sub pads being disposed in the same layer as the layers which are formed with the signal line of the signal via hole, or being disposed outside the layers which are formed with the signal line which is connected with the signal via hole.