PURPOSE: To smoothly execute removal of an air accompanying filling up of the material in a product part by positioning a forming gate at the side opposite to the gas venting part and near the outer wall of the bottom part from the end of the opening part in the cavity for product and above the outer wall part in the cavity for product.

CONSTITUTION: The forming gate 4 is positioned at the side opposite to an overflow gate part 6 and near the bottom part 3b from the end 3c of the opening part in the product part 3 and above the outer wall part 3a in the cavity for product. At the time of pouring the molten material 13 from the forming gate 4, this fills in the side part 3a and the bottom part 3b in the cavity 3 for product with good balance and at last, fills in an overflow part 7. Weld and blow hole are not developed in the bottom part 3b of the product part and the removal of an air is smoothly executed and the product having good quality is obtd.