An image forming device, which is included in an image forming apparatus, includes an image reader, a sheet conveyance passage, a transparent body, an opposing body, and multiple curved opposing portions. The image reader is configured to read an image formed on a target object. The sheet conveyance passage is a passage through which the target object is conveyed. The transparent body is disposed between the sheet conveyance passage and the image reader. The opposing body is disposed facing the transparent body on a side opposite the image reader. The multiple curved opposing portions have respective outwardly curving reference planes. The multiple curved opposing portions are sequentially switched and located at a predetermined image reading position at which the multiple curved opposing portions face the transparent body with a gap through which the target object passes the predetermined image reading position.