The hot pressing S340 bonds (compresses) the plurality of base sheets 310 and the bonding sheet 320 by applying heat and pressure thereto in a state where the plurality of base sheets 310 and the bonding sheet 320 have been stacked thereon. At this time, the hot pressing S340 bonds (compresses) the plurality of base sheets 310 and the bonding sheet 320 by pressurizing while heating it with the heat of the melting temperature or more of the thermoplastic bonding sheet 320.

Herein, the PE film used as the bonding sheet 320 has the melting temperature of about 138° C., and the PP film 312 used as the base sheet 310 has the melting temperature of about 165° C., such that the hot pressing S340 pressurizes while heating it at about 138° C. or more and lower than 165° C.

Therefore, the hot pressing S340 bonds (compresses) the base sheet 310 and the base sheet 310 by melting only the PE film as the bonding sheet 320 while preventing the PP film 312 as the base sheet 310 from melting.

The forming the through hole 330 S350 forms one or more through holes 330 penetrating the laminate bonded through the hot pressing S340. That is, the forming the through hole 330 S350 forms one or more through holes 330 for electrically connecting (i.e., electrically conducting) the electrode (i.e., the thin film seed layer 314 and the internal plated layer 316) formed on the base sheet 310 stacked on the uppermost portion thereof and the electrode formed on the base sheet 310 stacked on the lowermost portion thereof by punching the laminate.