To provide a distortion adjusting jig capable of reducing costs by reducing maintenance costs and the number of components.

This distortion adjusting jig 3 includes: an jig body 8 which comprises an upside insertion hole 4 for inserting an upside erection piece 1a, a downside insertion hole 5 for inserting a downside erection piece 2a, and a jack mounting hole 7 having a communication hole communicating with the upside insertion hole 4; and a jack member 9 which adjusts a vertical position by abutting on the upside erection piece 1a via the communication hole of the jack mounting hole 7. The upside insertion hole 4 is provided with an upper bolt 11 for performing the vertical positioning and fixing of the upside erection piece 1a with respect to the jig body 8, a pair of right and left bolts 13 for performing the horizontal positioning and fixing of the upside erection piece 1a, and the like. The downside insertion hole 5 is provided with a lower bolt 22 for performing the vertical positioning and fixing of the downside erection piece 2a with respect to the jig body 8, and a lower lateral bolt for fixing the downside erection piece 2a.