A multilayer core board 10 includes tapered first via hole conductors 51 extending from the outer surface of a first insulating layer 24 to conductive portions 42a of a power source layer 42, second via hole conductors 52 extending from the outer surface of a second insulating layer 26 to the conductive portions 42a of the power source layer 42, tapered third via hole conductors 53 extending from the outer surface of the second insulating layer 26 to conductive portions 40a of a ground layer 40, and fourth via hole conductors 54 extending from the outer surface of a center insulating layer 22 to the conductive portions 40a of the ground layer 40. The first via hole conductors 51 are tapered, and thus the interval distance to the adjacent first via hole conductor 51 is shorter than straight-shaped first via hole conductors, and thus the pitch of the first via hole conductor 51 at the positive pole side and the fourth via hole conductor 54 at the negative pole side can be sufficiently reduced. This point is applicable to the third via hole conductors 53.