A fabricating process for a substrate with an embedded passive component is provided. The fabricating process includes the following steps. First, a substrate including a top conductive layer, a bottom conductive layer, and at least a dielectric layer is provided. The top conductive layer and the bottom conductive layer are separately disposed on a top surface and a bottom surface of the dielectric layer. Next, a plurality of plating through holes is formed in the substrate. Then, the top and the bottom conductive layers are patterned to form a patterned top conductive layer and a patterned bottom conductive layer separately, and the dielectric layer is exposed in part. The patterned top conductive layer and the patterned bottom conductive layer have many traces and many trenches formed by the traces. Thereafter, the trenches are filled with a material, wherein the traces and the material are adapted for forming the passive component.