Abstract: A method of manufacturing an embedded-trace substrate is provided. A core plate, which comprises a central core, a first and a second thick resin layers respectively formed on top and bottom sides of the central core, is provided. Next, a through hole and a plurality of trenches are formed on the core plate, wherein the through hole passes through the core plate, and the trenches are formed on the upper and the lower surfaces of the core plate. Then, the core plate is subjected to one-plating step for electroplating a conductive material in the through hole and the trenches at the same time. Afterwards, the excess conductive material is removed from the upper and lower surfaces of the core plate so that the surfaces of the conductive material filling in the through hole and the trenches are coplanar with the surfaces of the first and second thick resin layers.