A printed circuit board includes a core insulating layer including an isotropic resin, a first circuit pattern filled in a circuit pattern groove at an upper portion or a lower portion of the core insulating layer, a first insulating layer provided in a top surface thereof with a circuit pattern groove and covering the first circuit pattern, and a second circuit pattern to fill the circuit pattern groove of the first insulating layer. A material, such as polyimide, having an isotropic structure is employed for the core insulating layer, thereby preventing the substrate from being bent without glass fiber. Since the glass fiber is not included, the buried pattern is formed at the upper portion or the lower portion of the core insulating layer, so that the thin substrate is fabricated.