The invention provides a transporting system and a transporting unit included therein. The transporting system includes a first rail including a first region and a second region, the first region being a region where the first rail extends linearly and the second region being a region where the first rail is curved. A second rail includes a third region, separated from the first region, and a fourth region overlapping the second region, wherein the first and second rails merge at a joining location that includes the second region and the fourth region. Optical lines are disposed in the second region and the fourth region, wherein the optical lines are parallel to each other in the fourth region. A first transporting unit travels on the first rail. A second transporting unit travels on the second rail. A first controller controls the traveling of the first and second transporting units using light transmitted or received through the optical lines.