PURPOSE: To eliminate the unnecessary die opening even when the molten metal into plural sets of casting machines is supplied in the preset order and to prevent the temp. drop of a die by controlling molten metal supplying demand time into a molten metal supplying device and cooling time of the casting machine.

CONSTITUTION: A travelling type molten metal supplying robot 2 is arranged as the molten metal supplying device in between a holding furnace 1 and plural sets of gravity casting machines 11-14. The molten metal supplying robot 2 is controlled with a controller 3 for robot by specifying the casting machine and a molten metal supplying program, etc., from an automatic molten metal supplying device 4. Casting machine control devices 21-24 control the casting movement of the gravity casting machines 11-14, respectively, and further, provide panels 31-34 which can beforehand specify the die to cast the product, and are connected with the automatic molten metal supplying device 4. A data setting machine 5 inputs data corresponding to the die and the fixed data, and is connected with the automatic molten metal supplying device 4. By this method, the die opening time is controlled and the quality is improved and the load of the worker is reduced.