PURPOSE: To shorten a change time, and to improve change workability by constituting a change cart so as to be runnable and transferable onto a billet loader, so that a mandrel can be changed by a transverse movement by the billet loader.

CONSTITUTION: After an ascending/descending rack base 26 on which a change cart 30 is loaded is allowed to ascend, the change cart 30 is run by a driving device provided on the ascending/descending rack base 26, and transferred to a billet loader 18. The connection of the driving device of the ascending/descending rack base 26 and the change cart 30 is detached, and the billet loader 18 is subjected to transverse movement along common rails 16, and stopped in a center position of the extruding press. By operating an ascending/descending handle of the change cart 30, centering an extruding stem 12 is executed, and from the extruding stem 12, a mandrel 14 is drawn out by removing its screw, and loaded onto the change cart 30. The billet loader 18 is moved to the extruding press side and returned to a stand-by position, and in a state that the mandrel 14 remains loaded, the change cart 30 is moved to the ascending/descending rack base 26. The mandrel 14 is carried over by a hoist, and thereafter, the ascending/descending rack base 26 is allowed to descend and returned to its initial state.