An image forming apparatus includes an image forming unit configured to perform a printing process of forming an image on a print medium based on print data, and a processor. The processor is configured to determine whether or not the printing process has completed based on remaining print data to be printed, when the print medium is removed from a paper discharge tray in which the print medium on which the image is formed by the image forming unit is placed, and to cause a warning to be output upon determining that the printing process has not completed based on the remaining print data to be printed.