According to an embodiment, when moving to the open state, the first structure 101 may gradually move away from the roller 151, and the second area A2 or the multi-joint hinge structure 113 may move to the outside of the second structure 102. For example, as the first structure 101 moves to the open state, the second area A2, along with the multi-joint hinge structure 113 connected to the first structure 101, may gradually be exposed to the outside of the second structure. When the first structure 101 slides, the roller 151 may rotate correspondingly and guide the multi-joint hinge structure 113 to the outside of the second structure 102. For example, while the multi-joint hinge structure 113 moves to the outside of the second structure 102 (or while being received in the second structure 102), the roller 151 may mitigate direct contact or friction between the multi joint hinge structure 113 and the second structure 102. According to an embodiment, since an end of the support sheet 153 is connected to the first structure 101, the support sheet 153 may gradually depart from the roller 151 and move onto the second structure 102 (e.g., the third plate 121c) as the first structure 101 slides. For example, the support sheet 153 may be deformed into a flat plate shape while gradually moving between the display (or multi joint hinge structure) and the second structure (e.g., the second plate 121a or the third plate 121c). When reaching the open state, the support sheet 153 may be disposed in an unfolded state inside (e.g., the rear surface) the display 103, for example, the second area A2. According to an embodiment, as the support sheet 153 gradually escapes from the roller 151, the gap (e.g., the arrangement gap G of FIG. 22) between the surface of the display 103 and the second plate 121a (e.g., the inner side of the edge) may gradually increase. For example, as the first structure 101 moves from the closed state to the open state, the gap between the surface of the display 103 and the second plate 121a increases, so that the second area A2 may move to the outside of the second structure 102 without causing the surface of the display 103 to contact or rub against other structures.