To provide a method for straightening a hat type steel sheet pile by which the change in the width of a material to be straightened in accordance with the alternation of rolling reduction can be suppressed without depending on shape adjustment of straightening rollers.

By using small rollers 3, 3A, 3B, 3C, 4, 4A, 4B which ascend and descend in accordance with the rolling reduction of the straightening rollers while restraining a flange part 12 by standing against the straightening rollers 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C which become the force points of three-point supporting repeat bending, the sheet pile is straightened while suppressing the change of the width of the material to be straightened in straightening.