An image forming apparatus an electrophotographic image forming section and a controller. The image forming section forms a toner image on a print medium. When a cumulative operation reaches a predetermined value, the controller causes the image forming section to form the toner image of a pattern image on the print medium. The pattern image is at least one of a number of pattern images aligned in an advance direction, the number of pattern images being increased in accordance with a cumulative print duty. The cumulative operation includes a number of print jobs, a number of printed pages, and a number of rotations of an image drum. The number of printed pages has a print duty less than a predetermined value.