To easily obtain a metal tube with excellent dimensional precision by increasing the pressurizing state of a metal tube interposed between the opposite flat faces, rolling it and reducing it into a prescribed diameter.

A flat plate tool 2 and a moving tool 3 are inclined and opposed. A metal tube 1 is interposed at the position expanded between the flat faces of the flat plate tool 2 and the moving tool 3. The moving tool 3 is moved in the direction of arrow mark. The metal tube 1 is rolled while being pressurized from the external face side between the flat plate tool 2 and the moving tool 3. Following the moving of the moving tool 3 in the direction of arrow mark, the interval between the flat faces of the flat plate tool 2 and the moving tool 3 is made small. The metal tube 1 is reduced, made into a prescribed diameter at the point a, it is corrected and the dimensional precision is improved.