A method for manufacturing coreless substrates is provided herein. The method first provides a base whose top and bottom sides are covered with metal layers respectively that are detachable from the base. From the two metal layers, the method then develops the bump-pad side or ball side wiring layers required by the coreless substrate simultaneously. The two metal layers along with their respective wiring layers are then separated from the base into two independent semi-products of the coreless substrate. The method then develops from the other sides of the two semi-products the laminate side wiring layers required by the coreless substrate.