A circuit substrate fabricating process includes a base layer, a patterned conductive layer, a dielectric layer, an outer pad and a conductive block. The patterned conductive layer is disposed on the base layer and has an inner pad. The dielectric layer is disposed on the base layer and covers the patterned conductive layer. The outer pad is disposed on the dielectric layer. The conductive layer is passed through the dielectric layer and connected between the outer pad and the inner pad, wherein the outer pad and the conductive block are formed as an integrative unit, and an outer diameter of the outer pad is substantially equal to an outer diameter of the conductive block. In addition, a fabricating process for the circuit substrate is also provided.