An image forming apparatus is connected to a host device including first and second power domains which are separately supplied with power and includes first and second memories to be disposed in the second power domain, a main controller disposed in the first power domain and to perform a control operation using the first memory in a normal mode, and a sub-controller disposed in the second power domain and perform a control operation using the second memory in a power-saving mode, where when the normal mode is changed to the power-saving mode a power supply to the first power domain is shut off, the first memory operates in a self-refresh mode, and the main controller copies central processing unit (CPU) context information into a context storage unit, and when the power-saving mode is changed to the normal mode, the main controller is booted using the CPU context information stored in the context storage unit.