There is provided a pattern inspection apparatus that is capable of detecting a defect accurately and efficiently to inspect a pattern of a semiconductor device. The pattern inspection apparatus includes: a contour extraction means for extracting contour data of a pattern from a captured image of the semiconductor device; a non-linear part extraction means for extracting a non-linear part from the contour data; an angular part extraction means for extracting an angular part of a pattern from design data of the semiconductor device; and a defect detection section that compares a position of the non-linear part extracted by the non-linear part extraction section with a position of the angular part extracted by the angular part extraction section so as to detect a position of a defective part of a pattern.