A wiring board of the present disclosure includes a core substrate, insulating layers, signal wiring conductors, ground wiring conductors, power-supply wiring conductors, a first mounting portion on which a first semiconductor device is to be mounted, a second mounting portion on which a second semiconductor device is to be mounted, many first-semiconductor-device connection pads connectable to signal electrodes of the first semiconductor device, many second-semiconductor-device connection pads connectable to signal electrodes of the second semiconductor device, and many signal connection conductors that connect the first-semiconductor-device connection pads to the second-semiconductor-device connection pads. The signal connection conductors include signal connection conductors of a first wiring group that extend only through a region above the top surface of the core substrate, and signal connection conductors of a second wiring group that extend through a region below the bottom surface of the core substrate.