A region-extraction method for extracting a contour of a desired region is provided.The method includes: a step (a) for displaying an image; a step (b) for selecting a desired region in the image; a step (c) for selecting an element graphic corresponding at least a partial contour in a partial region in the desired region; a step (d) for approximating the contour of a part of the element image to at least a partial contour in the partial region; a step (e) for repeating the steps (c) to (d) at least twice; and a step (f) for making a first contour by combining at least a part of elements after the approximation.