1. An apparatus for examining pattern defects comprising: a strain amount calculation unit that compares an observation image and a reference image which is obtained from design information, or an observation image which is different from the observation image so as to estimate a strain amount; a compensated image forming unit that forms a compensated image which is obtained by compensating one of the images which is used for the comparison using the strain amount; and an identification unit that compares the compensated image and the other of the images which is used for the comparison so as to identify the defect of a pattern.