Component built-in board and method of manufacturing the same, and mounting body

A method of manufacturing a component built-in board, the component built-in board being a component built-in board of multi-layer structure that has a plurality of unit boards stacked therein and is configured having a plurality of electronic components built in thereto in a stacking direction, the method comprising the steps of:

• forming a first wiring layer on both surfaces of a first insulating layer, forming a first interlayer conductive layer connected to the first wiring layer by penetrating the first insulating layer, and forming in the first insulating layer an opening in which the electronic component is to be housed, to produce a double-sided board as the unit board;
• providing a first adhesive layer on both surfaces of a second insulating layer and forming a second interlayer conductive layer that penetrates the second insulating layer along with the first adhesive layer, to produce an intermediate board as the unit board;
• and
• housing the electronic component in the opening of the produced double-sided board and stacking a plurality of the unit boards in the stacking direction,
• in the step of stacking, stacking such that the double-sided board is disposed in each of a layer above and a layer below the produced intermediate board.