PURPOSE: To obtain a circuit board wherein a plurality of conductor circuits have been brought into close contact with, and united to, an insulating part firmly by a method wherein a primary-side circuit molded product which has been molded by executing a plating treatment to a thermoplastic resin is held inside a metal mold in a pressure contact state and a secondary-side insulating part is injection-molded by using an insulating resin.

CONSTITUTION: A common electrode part 4a in a primary-side circuit molded product 4 to which a plating treatment has been executed is inserted into, and positioned in, a central hole 7b in a lower mold 7 in a secondary-side insulation part; after that, a metal mold is fastened. A surface pattern 4a and a rear-surface pattern 4b are held in a state that they are brought into pressure contact with the surface 6a of an upper mold 6 and with the surface 7a of the lower mold 7; after that, a cavity 5a is filled with PPS (polyphenylene sulfide) as an insulating thermoplastic resin from a gate part 7c. The common electrode part 4d is fractured from a notch-shaped part at the base part 3a of the common electrode part 4d and it is removed. A plurality of independent conductors are formed. As a result, plated layers 3 are formed on the surface pattern 4a and the rear-surface pattern 4b, and a circuit board 10c in which a plurality of independent conductor circuits have been united can be obtained.