An image-forming apparatus includes an image-forming section, a detection section, and a controller. The image-forming section has an image-bearing body on which an electrostatic latent image is formed and a developing unit that develops the electrostatic latent image. The detection section generates an output indicative of a remaining amount of toner in the developing unit. The controller drives the drive section to cause the image-forming section to move from one position to another, and determines a position of the image-forming section based on the output of the detection section. The detection section is mounted to a toner cartridge within the developing unit. When the image-forming section is moved from one position to another, the detection section receives light reflected by a high-reflectivity area and a low-reflectivity area, thereby detecting the position of the image-forming section.