A glasses-free three-dimensional display device comprising: a display device comprising a flat panel display; and a 3D viewing cover detachably disposed on the flat panel display, the 3D viewing cover configured to allow images displayed on the flat panel display to be viewed in three dimensions, wherein the display device comprises a cover setting program executable by the display device to set setting parameters of the 3D viewing cover wherein the 3D viewing cover comprises: a cover frame configured to be coupled to the display device, the cover frame comprising an opening corresponding to the flat panel display in a center portion thereof; a buffer member around the opening on an inner surface of the cover frame; a three-dimensional film fixed to the inner surface of the cover frame by the buffer member, the three-dimensional film covering the opening; and a transparent plate between the cover frame and the three-dimensional film characterized in that the buffer member is formed of an elastic member, the thickness of which decreases when a force is applied in a direction of the thickness of the buffer member, and which is restored to its original state when the force is removed, wherein when the 3D viewing cover is mounted on the display device, the buffer member may be compressed in a thickness direction of the buffer member, and when the 3D viewing cover is separated from the display device, a thickness of the buffer member may be expanded and restored to an original thickness and thereby the buffer member serves to absorb a manufacturing error of the cover frame and the mobile device so that the three-dimensional film may always be in close contact with the flat panel display of the device when mounted on the display device. a display device comprising a flat panel display; and a 3D viewing cover detachably disposed on the flat panel display, the 3D viewing cover configured to allow images displayed on the flat panel display to be viewed in three dimensions, a cover frame configured to be coupled to the display device, the cover frame comprising an opening corresponding to the flat panel display in a center portion thereof; a buffer member around the opening on an inner surface of the cover frame; a three-dimensional film fixed to the inner surface of the cover frame by the buffer member, the three-dimensional film covering the opening; and a transparent plate between the cover frame and the three-dimensional film characterized in that the buffer member is formed of an elastic member, the thickness of which decreases when a force is applied in a direction of the thickness of the buffer member, and which is restored to its original state when the force is removed, wherein when the 3D viewing cover is mounted on the display device, the buffer member may be compressed in a thickness direction of the buffer member, and when the 3D viewing cover is separated from the display device, a thickness of the buffer member may be expanded and restored to an original thickness and thereby the buffer member serves to absorb a manufacturing error of the cover frame and the mobile device so that the three-dimensional film may always be in close contact with the flat panel display of the device when mounted on the display device.