PURPOSE: To eliminate the need for changing set-up and to finish highly efficiently the tube hole of a waveguide by using the same die for inserting a mandrel and for extracting the mandrel.

CONSTITUTION: When a mandrel-extracting plate 30 is pressed down Z5 by driving a hydraulic press, a lower stopping pin 15 comes into contact with the lower surface of a stopping plate 24 to block the lowering of a mandrel plate 16 through a changeover stopper 23. Because upper stopping pins 31A are in a capable state of penetrating the stopping plate 24 and the mandrel plate 16, the mandrel-extracting plate 30 is lowered. Then, after penetrating push-pin holes 22, pushing pins 32 project lengthily downward from the mandrel plate 16, to press the upper surface of a flange 3A by its lower tip surface, and a waveguide 1 is pushed downward and is extracted from a mandrel 17.