To decrease the defects of glass products occurring in a ring mold and the impact at the time the ring mold seats on a lower die.

The oil pressure of a lower cylinder 13 pressing the ring mold 6 to the lower die 2 is changed at the time of releasing the pressure of an upper die 5. Further, the ring mold 6 is pressed by one set of the upper and lower cylinders 14, 13 joined back to back and the impact at the time of seating is decreased by controlling the relative position in the height direction of the ring mold 6 by the upper cylinder 14.