A sleeve type smart device comprises: a cylindrical flexible display panel which displays seamless continuous images on an outer surface thereof, and has a sleeve-shaped form of which the inside is empty; a sensing unit located at an inner surface of the flexible display panel so as to recognize an entity located inside the flexible display panel; a mode selection unit for automatically selecting an operation mode corresponding to the recognized entity; and a control unit for controlling so as to operate in the operation mode selected by the mode selection unit. Accordingly, the implementation of the seamless images is possible and one device could be used in various ways according to an installation state.