An image forming apparatus includes: an image forming unit configured to form an image on a continuous transfer medium based on a job; a controller configured to control the image forming unit, the controller having a function to cause the image forming unit to print information indicating a position mark which represents a position at least in a longitudinal direction of the continuous transfer medium on the continuous transfer medium and a function to acquire a result of reading of an image on the continuous transfer medium and determine a quality of the image on the continuous transfer medium based on the result of reading, wherein when an image is determined to be defective on the transfer medium having the position mark printed thereon, information on the position mark of the image determined to be defective is notified.