A vacuum casting apparatus of the type wherein a gate mechanism (12 and 10) is closed to form a seal. The interior of a cavity (6) is evacuated by a vacuum pump. The side of the gate mechanism (12 and 10) opposite to the cavity is filled with molten metal. The gate mechanism includes a ring-shaped groove (10e) having a V-shaped cross section positioned on the side opposite to the cavity which extends towards the sealing portion of the gate mechanism (12 and 10). With this arrangement, the molten metal in passage (8) fills the ring-shaped groove (10e) and enters the small clearance which exists in the sealing portion of the gate mechanism. The molten metal solidifies both within the ring-shaped groove (10) and this small clearance formed in the sealing portion. The resulting solidified metal piece has generally a ring shape that can be readily peeled off from the gate mechanism (12 and 10) following die release.