PURPOSE: To enable a large number of wiring patterns to be connected at a single joint so as to enhance a circuit board in density by a method wherein the wiring patterns provided to both the front and rear of the circuit board are connected through through-holes.

CONSTITUTION: Through-holes 14 are provided to a copper plated board 11 of glass epoxy resin or phenolic resin, the disused part of copper is removed through etching, and then wiring patterns 13 are formed on the front and rear of the board 11, resist is made to cover all the surface of the board excluding connection parts such as lands 12 or the like, and then gold plating is executed. All the wiring patterns 13 provided onto both the sides of the circuit board 11 are electrically connected together through the through-holes 14, and the lands located on both the sides of the board 11 are plated with gold. After a gold plating process is finished, a hole 15 larger than the through-hole 14 in diameter is punched with a press or bored with a drill so as to prevent a short circuit from occurring between the wiring patterns to shut off unneeded electrical conduction.