A wiring board with a built-in electronic component includes a core substrate, an electronic component in the substrate, a first upper-layer structure on first surface of the substrate, a second upper-layer structure on second surface of the substrate, and via conductors in the substrate and first upper-layer structure such that the via conductors are connected to an electrode of the component. The substrate has an accommodating layer, a first connection layer on first surface of the accommodating layer, and a second connection layer on second surface of the accommodating layer, the accommodating layer includes inner wiring and insulation layers and has cavity accommodating the component, the first connection layer includes inner wiring and insulation layers, and the second connection layer includes inner wiring and insulation layers such that the second connection layer includes greater number of inner wiring and insulation layers than the first connection layer.