A display unit includes a transparent light emitting element and displaying information on both sides thereof; a sensing unit for detecting the direction in which the screen of the display unit faces; and a controller for determining a placed state of the display unit according to the detected screen direction and changing information displayed on the display unit according to the determined placed state of the display unit. The screen direction may be one of a first direction in which a front surface of the display unit faces upward, and a second direction in which a rear surface of the display unit faces upward. By using the transparent display device, information can be displayed by using both surfaces of the display device, and displayed information can be changed according to a placed state of the display device. Thus, the users' interest and fun can be aroused and user convenience can be provided.