A component built-in board comprises stacked therein a plurality of printed wiring bases having a wiring pattern and a via formed on/in a resin base thereof, and comprises an electronic component built in thereto, wherein at least a portion of the plurality of printed wiring bases include a thermal wiring in the wiring pattern and include a thermal via in the via, at least one of the plurality of printed wiring bases has formed therein an opening where the electronic component is built, and has formed therein a heat-conducting layer and closely attached to a surface on an opposite side to an electrode formation surface of the electronic component built in to the opening, and the electronic component is fixed in the opening by an adhesive layer stacked on the heat-conducting layer, via a hole formed in a region facing onto the opening of the heat-conducting layer.