To prevent a track from being disrupted, to allow an unmanned carriage to travel as usual without waiting or searching for a detour route and to improve conveyance efficiency.

When an unmanned carrier 5 reaches a separation rail 10, the separation rail 10 is lowered, and a sub-rail 11 is horizontally moved and set in the gap of a disrupted branch rail 2. When the carry-in/out of a cargo to the unmanned carrier 5 is completed at a station 3, the separation rail 10 is again lifted with the unmanned carrier 5 mounted on it. The sub-rail 11 is horizontally moved to the original position interlockingly with the ascent of the separation rail 10. When the separation rail 10 is completely set to the branch rail 2, the unmanned carrier 5 starts a travel to a destination station.