An analysis method for a semiconductor device is described. The semiconductor device having an abnormal region is provided. Thereafter, a focused ion beam microscope analysis process is performed to the abnormal region, wherein the result of the focused ion beam microscope analysis process shows that the abnormal region has a defect therein. After the focused ion beam microscope analysis process, an electrical property measurement step is performed to the abnormal region, so as to determine whether the defect in the abnormal region is a device failure root cause or not.