In an image processing device, a contour image generation section extracts edge points according to image data acquired by an image acquiring section, and generates a contour image of a object formed out of the edge points; a first fitting line generation section conducts fitting of line of a predetermined shape to the object on the contour image according to the contour image, and generates a first fitting line; an effective edge point region generation section generates an effective edge point region in which the first fitting line has a width and a region in the line width is made to be the effective edge point region; and a second fitting line generation section generates a second fitting line formed out of a line of a predetermined shape according to the edge points in the effective edge point region on the contour image.