An image forming apparatus includes a photosensitive member, an exposure device, a detection device, a measurement device that measures a current flowing to the detection device, and a control unit that executes a detection mode in which an electrostatic latent image is formed on the photosensitive member and the measurement device detects a change in the current relative to the electrostatic latent image, wherein, in an adjustment mode, the control unit causes a potential difference between the electrostatic latent image and the detection device to be smaller as a layer thickness of the photosensitive member is more reduced.