To prevent such dislocations of automatically guided vehicles from their working positions as result from high-speed movement of robot arms.

An automatically guided vehicle 3 has a vacuum mechanism 9 for fixing the vehicle 3 at its working position by means of air suction force. The vacuum mechanism 9 comprises suction nozzles 10 placed on the bottom of the automatically guided vehicle 3 and having vacuum pads 11, elevating actuators 12 for moving the suction nozzles 10 vertically, a compressor 13, an air ejector 14, a drive valve 16 interposed in a drive line 15, an open valve 19 interposed in a branch pipe 18 branching from a suction line 17, and a controller 6 for controlling those elements. A memory 8 stores data indicating the need of countermeasures against dislocation at each working position, according to which data the vacuum mechanism 9 is actuated.