PURPOSE: To reduce the setting area and miniaturize the whole body of the device and reduce the weight, by making the projecting length of a curved rail shorter than that of a straight rail, in the movable rails of a branching and joining device.

CONSTITUTION: This branching and joining device is composed of three fixed rails 1, 2, and 3A, a movable straight rail 4, and a movable curved rail 5A bending a specific angle θ, the movable straight rail 4 and the movable curved rail 5A are slided interlocking through a mechanism, and a carriage 6 coming from the A side, for example, can advance in the direction B or C. And the fixed rail 3A is extended to the limit where the carriage 6 advancing from A to B or from B to A, and the fixed rail 3A are not interfered each other, and the projecting lengths of the movable straight rail 4 and the movable curved rail 5 are changed. That is, by making the movable curved rail 5 shorter by 1, its projecting length is made shorter 1cosθ. Consequently, the size c is made shorter 1sinθ, and the setting area can be made smaller a×1sinθ.