Abstract: A multi-stage helical gear manufacturing apparatus includes a first mold member, a second mold member, a large gear rotation core, a sleeve pin, a small gear rotation insert, and an insert pin. The second mold member moves the insert pin and the small gear rotation insert after the insert pin is caused to retreat in relation to the small gear rotation insert at the time of mold opening. The first mold member prohibits rotation of the large gear rotation core at the time of mold clamping, permits rotation of the large gear rotation core when the insert pin and the small gear rotation insert of the second mold member are moved at the time of mold opening, and causes the sleeve pin to advance toward the second mold member in relation to the plastic after the insert pin and the small gear rotation insert are separated from the plastic.