To provide a method, a machine and a unit for straightening shape steel, which achieves a mechanical straightening of H-steel or T-steel, providing reduction in the straightening time and an accurate and consistent straightening.

A pair of web pressing rollers 16..., and 18... is driven by hydraulic cylinders 15, 15 to hold a web 11a of the H-steel 11. Also a straightening roller 22 outside a flange and a pair of straightening rollers 26, 26 inside the flange are driven by protruding a rod 19a of a hydraulic cylinder 19 to hold both the transverse edges of the flange 11b. While holding that condition, an electric motor M rotates the roller 22 outside the flange to travel the H-steel 11 in the longitudinal direction of the web 11a, through which the H-steel is straightened. This results in the mechanical straightening of the H-steel 11 with a shortened processing time and with accuracy and consistency in quality.