A fast backward-jump type arc motion is observed with an arc running on rails. It is shown by the use of conductivity probes that this motion does not correspond to a continuous displacement of an ionized high-temperature region. The model of current transfer between two parallel arcs is adopted to explain the jump motion, for which a high rising speed of the arc voltage is a decisive factor. The current transfer is considered to be different from the re-ignition of a post-arc current.