To facilitate the bonding of the uniform thickness of plating without thickness unevenness having an adhesive insulating layer by setting the ten-point average surface roughness of a conductor foil at the weight-converted thickness in the specified range, and satisfying the maximum surface roughness under the specified conditions.

The ten-point average surface roughness Rz of a conductor foil is set at 30-60% of the weight-converted thickness. The maximum surface roughness Rmax is set so as to satisfy Rmax<Rz+5. On the roughened surface of the conductor foil, a metal, which can form the alloy with gold or can undergoes thermal fusion, is plated to the thickness of 0.3-5μm. Furthermore, the resin, which forms an insulating film after cooling by heating and fusing on the roughened surface of the conductor foil wherein the plating is performed, is formed at the thickness D satisfying Rz<D<Rz+5. Thus, the bonding for the uniform thickness without thickness uneveness having the adhesive insulating layer can be readily performed, and the productivity can be improved.