An image region extracting unit binarizes image data inputted from an image inputting unit and labels the binarized image data based upon a feature value of a pixel to be segmentized into a plurality of image regions. A contour connection determining unit 104 determines whether or not connection points connecting contour lines of the respective image regions extracted by a contour extracting unit each other exist. A contour modifying unit, when it is determined that the connection points exist by the contour connection determining unit, connects the contour lines each other at the connection points to modify the contour line.