To provide an image forming apparatus capable of supplying power according to a load state.

When it is determined that a power source is turned on, it is determined whether or not an option is attached (step S4). When it is determined that the option is attached, it is determined whether an inputted job requests a color mode or a monochrome mode (step S6). When it is determined that the color mode is requested, it is determined whether or not the inputted job includes scan processing (step S8). When it is determined that the job includes the scan processing in the step S8, it is determined that a copy mode is requested and thus it is determined that a mode for a color copy is requested (step S10). Then, the command of a power source output current is changed (step S12).