There is provided an image forming apparatus which is capable of quickly performing measurements required for obtaining a proper image density. The image forming apparatus having a plurality of image forming apparatuses performs an image density adjustment control process by carrying out a maximum density control process at a reference image forming speed, and carrying out a density gradation control process at each of the plurality of image forming speeds. Image forming conditions for carrying out the density gradation control process at speeds other than the reference image forming speed are determined by performing operation on image forming conditions determined by the maximum density control process carried out at the reference image forming speed.