PURPOSE: To enable repeated uses of a mold and effectively use the mold in the case of manufacturing plural pieces of products by fitting a runner parts, riser parts and feeder head parts as cores as changeable into a runner hole, riser hole and feeder head hole in the mold as reusable.

CONSTITUTION: After fitting the runner parts 4, riser parts 5 and feeder head parts 6 as the cores into the runner hole 3a1, riser hole 3a2 and feeder head hole 3a3 of a cope 3a in the mold 3 from the inside, the cope is combined with a drag 3b. Thereafter, by pouring molten metal from the runner parts 4, gas (the air) in the mold is exhausted from the riser parts 5 and also the molten metal is overflowed from the feeder head parts 6. After holding this condition for a fixed time, the cope 3a is drawn out while taking off the runner parts 4, riser parts 5 and feeder head parts 6. Successively, the product is taken out from the drag and the runner parts 4, etc., are broken to finish-work the product. By this method, the mold can repeatedly be used and effectively be used in the case of manufacturing the plural products.