An electronic device comprises a first structure including a first plate providing a first surface and a second surface and a second structure coupled to surround at least a portion of the first structure and configured to guide the first structure in a direction parallel with the first surface or the second surface. The device also includes a roller mounted on an edge of the second structure and a flexible display including a first area mounted on the first surface and a second area extending from the first area. The device also includes at least one support sheet mounted on the roller and wound around the roller as the roller rotates. The support sheet is wound around the roller when the second area is received inside the second structure, and is unfolded inside the second area when the second area is exposed to the outside of the second structure.