An image forming apparatus includes an auto document feeder, a scanner, a paper tray, and an image forming mechanism. The auto document feeder feeds an original sheet having an image and includes an original tray configured to load the original sheet having the image and a detecting mechanism configured to detect the original sheet set on the original tray. The detecting mechanism includes a terminal including a plane surface disposed to form a predetermined angle with respect to a sheet conveyance direction. The scanner scans the image on the original sheet fed by the auto document feeder to create image data. The paper tray supplies a recording medium. The image forming mechanism forms an image on the recording medium supplied from the paper tray with a developer according to the image data created by the scanner.