An index printer in which density correction can be reliably effected and in which an appropriate image can be printed is obtained. When a standard image data such as a so-called Bull's eye is input from an image memory to a gray image processing portion of a sub-control portion, data which is greater than a predetermined threshold value Q is extracted from the standard image data and is averaged so as to set a standard gray image. The set standard gray image is displayed on a whole surface of a display surface of a liquid crystal panel via a liquid crystal panel driver, and is printed onto a photographic printing paper by a light source.