[en] This research develops the quantitative evaluation technique for inside delamination of impact-damaged composite plate by Electronic Speckle Pattern Interferometry(ESPI). ESPI, one of optical inspection methods is the technique of non-contact, non-destructive, whole-filed measurement and recently the method is applied for non-destructive inspection of composite plate structure. However, there is some difficult to evaluate defects quantitatively. In order to extract the quantitative results, 2D displacement distribution and the first derivates of displacement are analyzed and defect sizes in each interlaminar are estimated from defect size in front and backside. The proposed ESPI technique for quantitative evaluation of inside delamination in composite material structure is expected as the advanced non-destructive testing method with the merits of time-saving and non-contact