PURPOSE: To enable an easy correction of a deformed pipe in a short time, by a method wherein a roll is supported at free ends of expanding objects so that the axial direction thereof always coincides with the axial direction of a center shaft.

CONSTITUTION: Split toroidal strips 15a, 15b, 15c, and 15d function as a rotating object having a variable radius, and produce frictions on a pipe A. Where expanding objects 3a, 3b, 3c, and 3d are spread radially with a slider 2 pushed in the arrow direction indicatd in the drawing, the pipe A is easily shifted to the direction of a long diameter even if a position relation of the pipe A and the split annuar strips 15b and 15d becomes oval. As a result, the pipe A coincides with a center shaft 1, the split annular strips 15a, 15b, 15c, and 15d being brough into contact with the pipe A, whereby the pipe A is corrected to the circularity. Since what comes in contact with an inner surface of the pipe A is the split annuar strips 15a, 15b, 15c, and 15d, the pipe A can be corrected without the production of convexities and concavities, even in the case of the pipe A being made of a soft material.