A display device includes a display unit, an external device interface unit configured to receive an image signal from a set-top box connected to the display device, and a control unit configured to, if a broadcast channel is changed, display a broadcast image of the changed broadcast channel based on the image signal received from the set-top box, to recognize the channel number of the broadcast image by using the displayed broadcast image, and to display broadcasting information related to the recognized channel number on the display unit.