A method and an apparatus of forming a multilayer printed circuit board which can positively remove voids in the prepregs in the printed board and enhance the reliability of the produced printed circuit board and is superior in economy, wherein a laminated assembly of a plurality of printed circuit board components and a plurality of prepregs alternately laminated on each other is sandwiched between upper and lower jig plates, and the laminated assembly sandwiched between the jig plates is clamped between heating plates of a bonding press to heat the assembly to a predetermined temperature, and, thereafter, a pressure is applied to the upper and lower jig plates so as to urge them against each other for bonding the printed circuit board component and the prepregs. An exterior pressurizing means is provided around the printed circuit board components and the prepregs sandwiched between the upper and lower jig plates in order to prevent the molten prepregs from flowing outwardly, thereby raising the fluid pressure of the molten prepregs to squeeze out air bubbles existing in the prepregs.