Provided are a method, an apparatus, and a program for processing a mammographic image, whereby the file size of the mammographic image can be remarkably reduced while retaining the original breast portion sufficient for diagnosis. A controlling unit divides an original mammographic image into a breast portion and a background portion based on a predetermined value (whether each pixel value of the original mammographic image is greater or smaller than a predetermined value). It determines the breast boundary line between the breast portion and the background portion (operation S2). It shifts and expands the breast portion upward, downward and forward to result in a secondary boundary line, wherein the breast portion side of the secondary boundary line has a size larger than that of the breast portion (operation S3). In addition, the controlling unit cutting off the background portion of the mammographic image vertically and/or horizontally at the secondary boundary line so that the original breast portion side remains, thereby obtaining the finally processed mammographic image (operation S4). Thus, the controlling unit generates the final image smaller in file size than the original mammographic image.