A semiconductor package molding device is provided. The semiconductor package molding device includes a chamber lower part which comprises a lower mold configured to receive a molding target, a chamber upper part configured to engage with the chamber lower part to isolate the inside of a chamber from the outside of the chamber, the chamber upper part including an upper mold configured to form a cavity with the lower mold, a first vent hole located between the chamber upper part and the chamber lower part, the first vent hole configured to discharge gas from the inside of the cavity after the chamber upper part and the chamber lower part engage with each other, a pot which is formed in the lower mold in the chamber lower part, a plunger configured to push up a molding material in the pot, a second vent hole which is formed in a side surface of the pot in the chamber lower part and a cavity vacuum pump configured to discharge gas through the first vent hole and the second vent hole.