A component built-in board, wherein at least two layers of a plurality of printed wiring bases are disposed on a rear surface side of an electronic component; the at least two layers of the printed wiring bases include a heat radiation-dedicated wiring pattern that is disposed above the rear surface of the electronic component; the heat radiation-dedicated wiring pattern is formed such that a heat radiation-dedicated wiring line and a signal-dedicated wiring line are continuous; a via includes a plurality of heat radiation-dedicated vias which connects the rear surface of the electronic component and the heat radiation-dedicated wiring pattern; and the heat radiation-dedicated wiring pattern is continuous from a place where connected to the heat radiation-dedicated via to be connected also to another via disposed at an outer peripheral side of the electronic component.