A pattern inspection apparatus is used for inspecting a pattern, such as semiconductor integrated circuit (LSI), liquid crystal panel, and a photomask by using an image of the pattern to-be-inspected and design data for fabricating the pattern to-be-inspected. The pattern inspection apparatus includes a reference pattern generation device for generating a reference pattern represented by one or more lines from design data, an image generation device for generating the image of the pattern to-be-inspected, a detecting device for detecting an edge of the image of the pattern to-be-inspected, and an inspection device for inspecting the pattern to-be-inspected by comparing the edge of the image of the pattern to-be-inspected with the one or more lines of the reference pattern.