A button processing method and a data processing apparatus that improve the operability of buttons when a display device with a display screen of small size is employed. In cases where an output image includes a button, when a display image is displayed on a display device with a small display device size, e.g., 6.5 inches, the size of the button in an image space is enlarged n times at a button enlargement ratio determined in accordance with the display device size. In contrast, when a display image is displayed on the display device with a larger display device size, e.g., 8 inches, the size of the button in an image space is enlarged, e.g., n/1.23 times at a button enlargement ratio determined in accordance with the display device size. That is, the smaller the size of the display screen of the display device, the larger the enlargement ratio of the size of the button in the image space, so that the button is displayed in predetermined size on the display device regardless of the display screen size of the display device.