PURPOSE: To perform sepn. of a cast part and a gate and runner part simultaneously with die opening by dividing a movable die to a movable body part and a movable sepn. part which is atached and detached to and from said part, and forming a cavity for casting and a passage for charging a casting material in the latter.

CONSTITUTION: A movable die 13 is divided to a movable body part 13a and a movable sepn. part 13b which is attached and detached to and from said part. A cavity 31 for forming the end ring of, for example, a rotor for an electric motor is provided on one surface side of the part 13b, and a gate plate 18 constituting a charging passage 32 for a casting material communicating with the cavity 31 is provided on the other surface side. A core 6 is first inserted into the die 13, and after the die 13 and a stationary die 20 are clamped, molten metal is charged through a charging port 7 and the plate 18 into the dies 13, 20, and a product 5 is formed. The dies are opened upon completion of forming, and the die 13 is retreated in a direction A. The plate 18 and the product 5 are cut and separated in this stage. A runner part 34 is ejected and removed with a piston rod 14. The need for cutting the runner part by a blade is thus eliminated and the productivity and quality of the product are improved.