A display system is disclosed. The present system comprises a display device and an image processing device, wherein the display device transmits a control signal for controlling an external image source device to the image processing device in response to a signal received from a remote controller, and the image processing device processes an image received from an image source device, transmits the processed image to the display device, and transmits the control signal received from the display device to the image source device. The image processing device identifies a state change of the display device in response to control signal transmission, and transmits a signal for changing an operation mode of the remote controller to the display device if no change is identified, and when the signal for changing the operation mode of the remote controller is received, the display device transmits the received signal to the remote controller.