In accordance with the distortion correction method for an X-ray radiograph diagnosis device, the distortion center of the X-ray image is determined by use of a plate-shaped object having a circular marker M and a marker center M.sub.0. On the basis of the positions of the sample points M.sub.1 through M.sub.4 upon the circular marker M, the distortion center is inferred. Further, a grid marker pattern is used to determine the magnitudes of pincushion distortion at respective distances from the distortion center. The correction coefficients for correcting the spool distortion at respective distances from the distortion center are determined on the basis of the relationship between the physical and displayed distances from the marker center M.sub.0 to the sample points.