The method of manufacturing a circuit board is capable of preventing deformation of a core substrate, ensuring size thereof and highly concentrating cable patterns so as to realize compact and high-performance semiconductor devices. The method of manufacturing a circuit board of the present invention comprises the steps of: forming a multilayered body, in which cable patterns on different layers insulated by an insulating layer are electrically connected, on a core substrate by a buildup process; and separating the multilayered body from the core substrate. A metal layer is vacuum-adhered on the core substrate. The multilayered body is formed on the metal layer by the buildup process and separated from the core substrate together with the metal layer by breaking the vacuum state between the core substrate and the metal layer