An image forming apparatus includes: a control unit configured to acquire base information by making a reading unit read a surface of the recording material with all image forming units set in a non-forming state, acquire first determination information by making the reading unit read a non-image region of the recording material with only a first image forming unit set in a forming state, and acquire second determination information by making the reading unit read the non-image region with all image forming units set in the forming state or with only all second image forming units set in the forming state. The control unit is further configured to determine a color of a toner adhered to the non-image region based on the base information, the first determination information, and the second determination information.