PRINTED WIRING BOARD

A printed wiring board includes a core substrate having cavity to accommodate an electronic component and including a front conductor layer formed on front side of the core substrate, and a back conductor layer formed on back side of the core substrate, through-hole conductors formed through the core substrate such that the through-hole conductors connect the front and back conductor layers of the core substrate, a front build-up layer formed on front surface of the core substrate and including interlayer insulating layers and conductor layers, and a back build-up layer formed on back surface of the core substrate and including interlayer insulating layers and conductor layers. The conductor layers in the front build-up layer include a conductor layer sandwiching one of the interlayer insulating layers with the front conductor layer such that the conductor layer and the front conductor layer have the same electric potential in region surrounding the cavity.