An image forming apparatus comprising: a volatile memory; and an SoC part configured to operate using the volatile memory in a normal mode, and configured to copy and use information stored in the volatile memory to an internal memory by switching to power saving modes in stages according to an external signal input to the SoC part, and configured to access the volatile memory when returning to the normal mode, wherein the SoC part comprises: the internal memory; a CPU for accessing the volatile memory in the normal mode; an interface part for receiving the external signal; and a control part configured, when the interface part has no input during a first preset time, to copy information stored in the volatile memory to the internal memory and to convert from the normal mode to a first power saving mode in order to lower an operating frequency of the volatile memory and an operating frequency of the CPU, and when a normal mode switch signal is not input during a second preset time in the first power saving mode, the control part is configured to control the CPU to access the information copied to the internal memory and convert from the first power saving mode to a second power saving mode to change the volatile memory from the normal mode to a self-refresh mode, characterised in that in the second power saving mode, the CPU is configured to operate using the information copied to the internal memory. a volatile memory; and an SoC part configured to operate using the volatile memory in a normal mode, and configured to copy and use information stored in the volatile memory to an internal memory by switching to power saving modes in stages according to an external signal input to the SoC part, and configured to access the volatile memory when returning to the normal mode, wherein the SoC part comprises: the internal memory; a CPU for accessing the volatile memory in the normal mode; an interface part for receiving the external signal; and a control part configured, when the interface part has no input during a first preset time, to copy information stored in the volatile memory to the internal memory and to convert from the normal mode to a first power saving mode in order to lower an operating frequency of the volatile memory and an operating frequency of the CPU, and when a normal mode switch signal is not input during a second preset time in the first power saving mode, the control part is configured to control the CPU to access the information copied to the internal memory and convert from the first power saving mode to a second power saving mode to change the volatile memory from the normal mode to a self-refresh mode, the internal memory; a CPU for accessing the volatile memory in the normal mode; an interface part for receiving the external signal; and a control part configured, when the interface part has no input during a first preset time, to copy information stored in the volatile memory to the internal memory and to convert from the normal mode to a first power saving mode in order to lower an operating frequency of the volatile memory and an operating frequency of the CPU, and when a normal mode switch signal is not input during a second preset time in the first power saving mode, the control part is configured to control the CPU to access the information copied to the internal memory and convert from the first power saving mode to a second power saving mode to change the volatile memory from the normal mode to a self-refresh mode, characterised in that in the second power saving mode, the CPU is configured to operate using the information copied to the internal memory.