A guide device for an A.G.V. in which a magnetic field generated around a guide cable is detected by a pair of detection coils at both sides of the guide cable, and wheels are steered and driven in accordance with the detected output from the detection coils. A pair of detection coils are arranged to follow the movement of the wheels to be steered in such a manner that the detection coils are disposed away from each other at a predetermined distance from the guide cable when the A.G.V. runs a straight portion of a course, while the detection coils are positioned closer to the guide cable when the A.G.V. runs a curved portion. As a result, when the A.G.V. runs the straight portion, the sensitivity with respect to the deviation between the detection coils is kept low so that the carrier can run smoothly, when the A.G.V. runs a curved portion, the sensitivity with respect to the deviation between the detection coils is increased. Consequently, operating performance such as high speed operating performance and the minimum turning diameter can be improved.