An image forming apparatus is provided. The image forming apparatus includes an electric power supply, a plurality of modules, a startup time calculator, and a fastest startup pattern determiner. The plurality of modules include a plurality of direct current (DC) modules and at least one alternating current (AC) module, and the modules are to be driven by an electric power supplied from the electric power supply. The startup time calculator calculates a startup time of each of the modules. The fastest startup pattern determiner determines a fastest startup pattern based on the startup time of each of the modules calculated by the startup time calculator, and starts up the modules in accordance with the determined fastest startup pattern. The fastest startup pattern is determined based on a longest startup time among the startup times of the DC and AC modules.