CIRCUIT BOARD

Provided is a circuit board capable of dissipating heat at a higher efficiency compared with conventional cases from an electronic component mounted at a high density. A circuit board has a first wiring layer and a second wiring layer, which are laminated on the front surface side of an aluminum base material. The second wiring layer is positioned between the first wiring layer and the base material. The first wiring layer is provided with a land having a BGA placed thereon and connected thereto, said BGA being a terminal of a wafer-level chip-size package. The land is electrically connected to the second wiring layer by means of a via-filling plating formed at a position overlapping the land when viewed from the lamination direction Z. Heat of the wafer-level chip-size package is transmitted to the base material via the land, the via-filling plating, and the second wiring layer, and is dissipated from the base material.