PURPOSE: To evacuate forcibly the gas in the cavity of a die by utilizing compressed air and to improve the performance of an evacuating device for the die by connecting an evacuating pipe via a conduit to the discharge port of the die device provided with a stop valve in the discharge port of a discharge passage communicating with the cavity.

CONSTITUTION: The gas in the cavity of the die 40 communicates with the discharge port 70 of a cylinder 50 via bypass passages 44, 46 prior to pouring of a molten metal into the cavity of the die. The gas guided to the inside of the evacuating pipe 72 is forcibly discharged by a Venturi effect when the compressed air is supplied to an injector pipe 74 by operating a selector valve 76. When the molten metal is poured into the cavity, the molten metal filling the cavity intrudes into the discharge passage 42 and the molten metal having prescribed inertia force contracts with the head part 54 of a valve 52. Then the valve 52 moves upward to close the discharge port 48 and prevents the outflow of the molten metal to the outside of the die when the inertia force of the molten metal overcomes the closing and holding force of the valve 52.