PURPOSE: To secure the insulating property between the adjacent pads, and to improve the peeling strength of a connection pad by a method wherein the tip part to be inserted into a connector is insulated.

CONSTITUTION: When a plurality of conductors 20 are formed in parallel on an insulated substrate 1 by etching, the coupling conductor parts 8, with which all the adjacent conductors 20 will be connected to arbitrary positions, are etched in such a manner that the dimension a-component is masked so that the tip of the conductors 20 is not exposed as far as to the circuit end part. Then, after the electrode 7 for electroplating has been connected to one end of the coupling conductors 8, an over-coating 30 is provided in such a manner that the coupling positions of connection pads 50 and the coupling conductors 8 will be opened. In this state, after the prescribed plating has been conducted on the connection pads 50 by applying a current to the electrode 7 of the coupling conductors 8, the coupling conductor pads 8 only, with which the connection pads 5 are connected, is removed by etching. In this case, the plating formed on the connection pads 5 functions as an etching resist. Lastly, the electrode 7, which is used for plating, is cut from the edge face.