1. An image processing method for processing an image of an optic disc region in a photographed ocular fundus, comprising: extracting a disc region; dividing the disc region into a plurality of regions by a plurality of dividing lines that extend radially from the center of gravity of the disc region; radially scanning the divided regions from the center of gravity while angles are shifted in order to detect in each individual region a point at which luminance variation reaches a maximum; and determining a contour line of the disc region based on the detected points at which luminance variation reaches a maximum.