To provide a method of current collection without slip of contacts at rolling contact, and with little fluctuation of electric resistance due to slip or the like, since a constant strong pressure can be put on it at all times.

A conductive planet ring is characterised in that it is endowed with elasticity and having a diameter larger than the gap between an inner ring and an outer ring of a concentric conductor is inserted into the gap. The mechanism of the planet ring elliptically compressed by rotation of the outer ring or the inner ring (or a relative rotation in case the both rings are rotated) of making a rolling sun-and-planet motion around an axis while insulation displacing between the both rings at all times by repulsive force coming from the the planet ring elliptically compressed makes use of parts insulation displaced between the both conductive rings and the planet ring as electric contacts.