PURPOSE: To prevent bend of a bending tool with a simple means, for the purpose of producing a pipe with precise dimension and high quality, by arranging the lower piston/cylinder units between the table supporting the lower bending tools and the lower cross-piece.

CONSTITUTION: The upper and lower piston/cylinder units 7, 8 are connected to each other via a pressure medium line, or the lower piston/cylinder units 8 can be energized individually. In order to realize that, an H-beam 12, which is a beam frame having a large bending strength, is arranged between the table 10 and the cross-piece 5 of the frame, with both ends of the H-beam 12 supported in the side columns. The H-beam 12 cooperates with a gap- measuring device 14 for detecting a gap between the H-beam 12 and the table 10 of the lower bending tools 9. The change in the gap is a yardstick for the bending of the table 10, and is compensable through the energization of each piston/cylinder 8, enabling the accurate positioning of the table 10 to be guaranteed.