The image forming apparatus includes a process unit, a latent image writer, a power source, and a controller. The process unit is detachably attachable relative to the image forming apparatus and includes, as a single integrated unit, a latent image bearing member to bear a latent image on a surface thereof, a charging device to charge the surface of the latent image bearing member, and a development device to develop the latent image with toner. The controller causes the power source to output a charging bias at a predetermined target level supplied to the charging device. The process unit includes a first storage device to store correction information for calculating the predetermined target level of the charging bias in accordance with a combination of the latent image bearing member and the charging device. The controller corrects the predetermined target level based on the correction information in the first storage device.