A portable device having a display, the display including a main surface area, a first curved surface area extending from a first side of the main surface area, and a second curved surface area extending from a second side of the main surface area that is opposite the first side, a sensor configured to detect a state of the portable device, and a controller configured to control the display to display a user interface (UI) on one of the first curved surface and the second curved surface based on the state detected by the sensor.