Image forming apparatus, additional apparatus, and control method thereof

An image forming apparatus, an additional device, and a method for controlling the additional device are provided to supply power to only an additional device required for the image forming apparatus to reduce power consumption. An image forming apparatus(100) operating in a normal mode and a power-saving mode includes a signal receiver(110), an interface(130) connected with a predetermined additional device(200), a detector for detecting whether the additional device is connected with the interface, and a controller(170). The controller outputs a power-saving signal having power-saving mode information to the additional device connected with the interface through the interface when the image forming apparatus operates in the power-saving mode. The controller outputs a normal signal having normal mode information for operating the additional device in the normal mode to the additional device through the interface when a predetermined input signal is received through the signal receiver.