To provide an image forming apparatus for which a low-voltage power source having a small current capacity can be used by controlling peak of current consumption in a printer.

A current detection circuit is arranged in a power source line to which a plurality of units are connected, a starting current flowing at the start-up of each unit is measured by the current detection circuit, then, by controlling the unit start-up timing based on the measurement results, the peak of the current consumption due to the overlapping of the starting current is controlled.