A display device includes a display panel including a plurality of pixels and outputting an image through a first surface; and a first polarizer attached to the first surface of the display panel, the first polarizer transmitting linearly-polarized light of a first direction and reflecting linearly-polarized light of a second direction perpendicular to the first direction, wherein when a voltage is not applied, the display device is used as a mirror mode and the first polarizer reflects external light, and when a voltage is applied, the display device is used as an image display mode and an image from the display panel is outputted through the first polarizer.