An edge extraction unit extracts vertical and horizontal wiring edges and slanted wiring edges from overall wiring graphics, and a wiring width classification unit executes a scaling process for the overall wiring graphics to classify the wiring graphics into wiring width ranges which are divided by a predefined reference wiring width. A vertical and horizontal wiring edge extraction unit extracts the vertical and horizontal wiring edges which are in contact with graphics classified into the wiring width ranges, and a vertical and horizontal wiring interval verification unit verifies intervals between the vertical and horizontal wiring edges and opposed edges to be verification counterparts based on a vertical and horizontal reference interval for each wiring width range. A slanted wiring edge extraction unit extracts slanted wiring edges which are in contact with graphics classified into the wiring width ranges, and a slanted wiring interval verification unit verifies intervals between the slanted wiring edges and opposed edges to be verification counterparts based on a slanted reference interval for each wiring width range.