A display device includes a flexible display including a flexible display panel and a flexible touch panel, and a housing configured to enclose the flexible display while allowing the flexible display to move relative to the housing such that a portion of the flexible display is drawn out of the housing and retracted into the housing. The display device further includes a marker configured to contact a location of the flexible touch panel when a portion of the flexible display is drawn out of the housing. The marker is provided such that the contact location changes as the flexible display moves relative to the housing. The display device also includes at least one processor configured to compute the contact location on the flexible display and to adjust the size of an image displayed on the flexible display panel based on the computed contact location.