PURPOSE: To prevent occurrence of tightening and galling of a casting to an insert by making the insert movably toward running-away direction from the casting in a cavity in a die casting machine, in which uses the insert in the cavity formed by die clamping.

CONSTITUTION: The cavity 21 is formed by clamping a movable die 19 and a fixed die 18. Next, the insert 37 is slided and the end part is projected into the cavity 21 to stop at the prescribed position. The molten metal is pressed in, filled up and solidified into a cavity 21 under this condition, to form the casting 31. During this, press-in of the molten metal is detected and after passing the fixed time till the molten metal is solidified only at contacting position with the dies 18, 19 and the end part of the insert 37 to run away the inert 37 from the cavity 21. By this method, the prescribed gap 31b is surely formed between the end parts of the casting 31 and insert 37. Therefore, the tightening of the end part of the insert 37 by the casting 31 is prevented, and in case of taking out the casting 31 by an ejecting pin 29 and even in case the casting 31 is rotated, the occurrence of the galling to the end part of the insert 37 is prevented.