PURPOSE: To improve the quality and yield of a pipe by providing plural supporting bodies holding a mandrel and die by centering coaxially and closing the space communicating to an annular space by moving these supporting bodies as well.

CONSTITUTION: A recessed groove 7 is formed in the orthogonal direction with a mandrel 3 on the rear end face of a bolster 7a and supporting bodies 11l, 11r in thick rectangular shape are arranged therein. A glass disk G is arranged in the storing part 1a of a container 1 to charge the mandrel 3 onto the inner face of a hollow billet H by a cylinder 8. The tip of the mandrel 3 is advanced to move the supporting bodies 11l, 11r and the mandrel 3 is held on the center line of a die 2 at the tip recessed place. In this case, the annular space between the mandrel 3 and die 2 is closed and the billet H is worked. Due to the misalignment of the mandrel 3 being prevented the quality and yield of a pipe are surely improved.