An electronic component built-in multi-layer wiring board that is configured by collectively stacking a plurality of printed wiring boards therein by thermal compression bonding and that has a plurality of electronic components built in thereto, wherein the electronic components include a first electronic component and a second electronic component having a thickness which is greater than that of the first electronic component, the first electronic component is built in to an embedding-dedicated board set to a thickness which is 80% to 125% of the thickness of the second electronic component, and the embedding-dedicated board and the second electronic component are then mounted on the printed wiring board and thereby built in to the electronic component built-in multi-layer wiring board, and the embedding-dedicated board is formed by an identical material to that of the printed wiring board.