PURPOSE: To obtain an extruded material for holding a high degree of vacuum, and having quality by stopping temporarily a container, preventing air intruding from between a die and a die ring for fitting and supporting the die, and exhausting the air in the container from a clearance between the die end face and the container.

CONSTITUTION: The die side end face of a container 1 is stopped in a state that a clearance 6 of, for instance, about 2-3mm exists against the die 3 face. In this case, since a seal ring 11 presses a die ring 5, the die ring 5 moves, for instance, by 0.2mm (C2) in the extrusion direction of a billet 13, and in a state that a stepped projecting part of the die ring 5 and a stepped recessed part 3a of the die 3 are subjected to face sealing by abutting, the billet 13 is charged into the container 1 by an advance operation of an extrusion stem 14, and the tip face of the billet 13 is pressed against the die 3. The extrusion stem 14 further advances and starts upsetting. When this state is continued, around the time when the billet 12 of the extrusion stem 14 side adheres closely to the container 1, air in a deaeration space 31 passes through the clearance 6 and is absorbed from the die 3 side by an operation of a vacuum tank 20.