A substrate with a built-in capacitor includes an insulating base material layer, a build-up layer formed on the insulating base material layer and including a conductor layer and an insulating layer, and a multilayer ceramic capacitor positioned in an opening of the base material layer and including internal electrodes, ceramic dielectric layers and a pair of external electrodes. The ceramic capacitor has a cuboid shape having long sides and short sides, the pair of external electrodes is formed on opposing long-side sides such that the external electrodes are separated by a distance in range of 30 μm to 200 μm and that each external electrode includes a conductive paste layer connected to a respective group of the internal electrodes and a copper plated layer covering the conductive paste layer, and the conductive paste layer includes Ni paste or Cu paste including glass component in range of 5% to 40%.