An image forming apparatus which forms a halftone image on a print medium by using a multipass process to scan a printhead N (N is an integer of 2 or more) times in a single area on the print medium and form dots by each scan operation includes a pass division unit which sets the print density of a scan operation in the first pass so as to prevent dots from overlapping with each other on the print medium, and sets the print densities of scan operations in the second to Nth passes, a tone reduction unit which generates print data of the respective scan operations in accordance with the print densities set by the pass division unit, and a printhead which prints a halftone image on a print medium on the basis of the print data generated by the tone reduction unit.