PURPOSE: To give a mechanism serving as a robot arm to a transport vehicle by shifting a mounting bed section for holding respective sensors and conveyer members between production facilities so as to lift the mounting bed section relatively to a movable car body according to the height of a carrying-in and -out port provided between the movable car body and mounting bed section.

CONSTITUTION: A transport vehicle 1 having workpieces W2 previously mounted thereon is shifted to a device A along a guiding conductor 5 and stopped by a guide path detecting sensor SF according to a travelling control display mask m1. Next, the height of a carrying-in and -out port of the device A is judged by a distance sensor S1 to locate a mounting bed 2 to the height of the device A according to the judgement. When the workpiece w1 on the device A is pushed out to the mounting bed section 2 to be stacked, the transport vehicle 1 is shifted to a device B. When the transport vehicle 1 arrives at the device B, it is driven by a distance sensor S2 until the mounting bed section 2 and the carrying-in and -out port of the device B have the same heights, so that the transportation can be carried out without needing a robot arm.