An image forming apparatus includes an image carrier and a detection unit. The image carrier is stretched around a plurality of rolls. The detection unit detects a density of a toner image formed on the image carrier, based on an amount of regularly reflected light from a surface of the image carrier. A detection length where the detection unit performs the detection in a movement direction of the image carrier is longer than a length, in the movement direction of the image carrier, of a deformation area where a deformation of the image carrier is caused.