An apparatus for fabricating semiconductor packages may include a thickness measurer configured to measure the thickness of a printed circuit board (PCB); mold dies, clamped to the top and the bottom of the PCB, through which a molding compound may be injected; and a pressure controller configured to control a clamp pressure of the mold die in response to the thickness of the PCB. The thickness of the PCB may be measured before molding the PCB, and a clamp pressure corresponding to the measured thickness may be decided. Therefore, it is possible to adjust the thickness variation of a PCB in real time, as they are being produced, to decrease the number of bad packages.