PURPOSE: To easily detect a normal stop at an end and midway abnormal stop by a method wherein a detecting contact point provided on a self-propelling device travels in keeping contact on an electric pole for detecting movement which alternately arranges current-carrying parts and noncurrent carrying parts.

CONSTITUTION: When a detecting contact point 11 provided on a self-propelling device 4 travels in keeping contact on an electric pole 7 for detecting movement which alternately arranges current carrying parts 8, 8a, etc., and noncurrent carrying parts 9, 9a, etc., in the travelling direction of the self-propelling device 4, the signals of two states of turning on or off electricity between the electric pole 7 for detecting movement and an electric feeder 5 are periodically produced. A detecting circuit 13 detects the potential difference of a resistance 14 provided between the electric pole 7 for detecting movement and the other electric feeder 5a, as the signal, and judges that the self-propelling device is travelling when the signal is periodically varied within a specified period of time and it is not travelling when the signal is not varied. When a power controlling part 12 receives a stopping signal, it stops supplying the power to both electric feeders 5, 5a, and stops the self-propelling device 4.