Abstract: A method for manufacturing circuit board includes steps of forming upper and lower copper foil layers on upper and lower surface of a PI substrate, respectively, etching the upper and lower copper foil layers to form first and second electrical circuits, attaching first and second PI coverlays to the upper and lower copper foil layers, respectively, etching the PI substrate through a PI etching process to form at least one opening exposing the lower copper foil layer, and performing a surface treatment to form a solder layer electrically connected to the electrical circuit of the lower copper foil layer for soldering electrical elements in a subsequent process. Therefore, the circuit board with double side circuit and single side assembly is obtained. The present invention do not employ the process of exposure ink, thereby simplifying the whole manufacturing procedure and greatly improving preciseness of the circuit board.