PURPOSE: To provide a three roll piping mill provided with forming mill rolls which can move in the radial direction.

CONSTITUTION: This mill provides forming mill rolls 2 arranged at an interval of nearly 120 degrees in the circumferential direction of a formed pipe 1, three roll axis cases 6 which are held so that rotation axes 4 of the mill rolls are supported respectively rotatably, an inner housing 8 supporting the roll axis cases so that they can move in the radial direction and an outer housing 10 which contains the inner housing freely attachably and detachably in the length direction of the pipe and is fixed to the outer part. Further, it provides three rolling down cylinders 12 moving the roll axis cases respectively in the radial direction, connects one end 14a with one end of the rotation axis so that it can oscillate freely and the other end with a rotation drive device and provides three spindles 14 penetrating the inner housing and the outer housing.