To automatically couple and decouple the carriage with and from the unmanned travel vehicle which is traveling by providing the traction device with a coupling and decoupling mechanism which lifts the tip side of a traction lever and drawing it out of the coupled tool and positioning member of the carriage.

The traction device 10 is provided with the coupling and decoupling mechanism which lifts the tip side of the traction lever 11 and draws it out of the coupled tool 8 and positioning member 17 of the carriage and is driven by an arm 21 for decoupling. When the unmanned travel vehicle 2 reaches the destination position of the carriage, a roll 22 of the decoupling arm 21 which is provided downward outside the body of the unmanned travel vehicle 2 abuts against a decoupling member 9 installed at the same destination position to cause the arm 21 to rotate by a certain angle of rotation. The rotation is transmitted as the rotation of a disk cam 20 through a rotary shaft 19 and the disk cam 20 is lifted to push up and draw the traction lever 11 out of a cut part of the positioning member 17 and also decouple the lever from the coupled tool 8 of the carriage at the same time.