A pattern edge detecting method includes: detecting edge points in an image of an inspection pattern acquired from an imaging device; generating a plurality of edge lines from the edge points using a grouping process; generating a plurality of edge line group pairs, each composed of a combination of first and second edge line groups to be a candidate of any of one and the other of an outside edge and an inside edge of the inspection pattern, the generated edge lines being divided into two parts in different manners; performing shape matching between the first and second edge line groups for each edge line group pair; and specifying, as an edge of the inspection pattern, one of the first and second edge line groups constituting the edge line group pair whose matching score is best of matching scores of the edge line group pairs obtained during the shape matching.