A display device which displays an image having a size corresponding to a display area exposed outside a housing is disclosed. In one aspect, the display device includes a flexible display panel having a recognition pattern, a housing, and a light-receiving sensor. The recognition pattern includes a plurality of self-luminous indicators arranged according to a first direction, and having different colors or different light-emitting intensities. The housing is coupled to the flexible display panel for entering/discharging of the flexible display panel according to the first direction such that a display area of the flexible display panel is variously exposed. The light-receiving sensor is positioned corresponding to the recognition pattern in the housing and respectively recognizes a plurality of indicators to sense the exposed display area of the flexible display panel.