An image extracting method includes: acquiring a scan image; generating a binary image of the acquired scan image and detects connected pixels in the generated binary image; setting up a circumscribed rectangle for the detected connected pixels; performing, in each side of a circumscribed rectangle, scan in a direction perpendicular to the side so as to detect edge pixels, wherein the scan starts at a plurality of points on a line, and the line extends to one vertex of the side, from a contacting point at which the connected pixels and the side contact; determining whether the detected edge pixels are located in a contour part of the object reproduced in the scan image; setting up a rectangular region based on the edge pixels determined as being located in the contour part of the object; and extracting an image from the set-up rectangular region.