An electronic component built-in substrate includes an insulating base material having a first surface and a second surface opposite to the first surface, an electronic component embedded in the insulating base material and having an electrode on a side surface thereof, a first wiring layer embedded in an area outside the electrode of the electronic component in the insulating base material with a surface of the first wiring layer being exposed from the first surface of the insulating base material, a via conductor reaching from the second surface of the insulating base material to a side surface of the electrode of the electronic component and the first wiring layer, and a second wiring layer formed on the second surface of the insulating base material and connected to the via conductor.