PURPOSE: To prevent bending at a tube end part by stably positioning a mandrel forming part by projecting the mandrel forming part in front of the forming part of an extrusion die in proportion to a speed of an extruded tube at the time of a tube end forming in initial extrusion.

CONSTITUTION: A billet 1 is inserted into a cylinder 9 and a mandrel 3 is inserted into the billet 1 at a speed nearly equal to an extrusion speed of an extruded tube 4 at initial extrusion to stably put the mandrel 3 in a prescribed position in front of a forming opening part 5 and then the billet 1 is extruded. The billet 1 is pressed by a ram 8 and is extruded through a gap between the forming opening part 5 and a mandrel forming part 6 to produce the extruded tube 4 having a hollow. Thus, bending at the extruded tube top part is prevented.