To prevent the mixing of overflowed molten metal into an adjoining mold in the case of being excess supplemental quantity of the molten metal into a pouring box and the leakage of the molten metal and the collapse of a mold caused by one side hitting of a sprue cup even in the case of developing the positioning error of the pouring box by forming a recessed type level-down part surrounding a runner on the upper surface of the mold and making the contact surface with the bottom part of the pouring box the almost horizontal surface.

The size of the sprue cup 50 in the mold 4 is e.g. 180mm width, 180mm length and 30mm depth and has the vol. of about 7kg as molten spheroidal graphite cast iron. At the center of this sprue cup 50, e.g. the runner 5a having 50mm diameter is opened and the sprue cup is connected with a cavity through the runner 5a. When a molten metal pouring nozzle 1a having e.g. 110mm outer diameter and 80mm inner diameter contacts with the mold 4, a molten metal passage fully covering the runner 5a and communicated with the nozzle, is formed (A). In the case the supplemental quantity of the molten metal into the pouring box 1 is excessive, the molten metal 7 is overflowed (B), but the molten metal is not flowed into the following mold 4.