The method of an embodiment includes the steps of: obtaining a first rocking curve with respect to a wafer obtained using an X-ray diffraction device; setting an X-ray incident angle range having a higher intensity than a reference level in the first rocking curve, calculating an inter-plane spacing for the set X-ray incident angle, calculating a strain value of the wafer using the calculated inter-plane spacing, and calculating sampled strain values on the basis of the calculated strain value; modeling a thickness according to the degree of damage of the wafer on the basis of the intensities of X-ray diffraction beams corresponding to the sampled strain values; obtaining a second rocking curve on the basis of the set X-ray incident angle range, the calculated inter-plane spacing, the sampled strain values and the modeled thickness; matching the second rocking curve to the first rocking curve by changing at least one of the X-ray incident angle range, the inter-plane spacing, the sampled strain values and the modeled thickness; and calculating the depth of damage of the wafer on the basis of the matching result.