An electric power feeding apparatus for feeding electric power to an electric device installed in a vehicle slide seat and movable together with the slide seat as the slide seat slides along a slide rail includes a cable rail disposed in parallel juxtaposed relation to the slide rail with a clearance defined therebetween, a power feeding cable disposed in the cable rail and fixed at one end to the cable rail, an opposite free end portion of the power feeding cable being drawn out from the cable rail into the clearance and extending upward through the clearance toward the slide seat for electric connection with the electric device, and a support member extending downward from the slide seat into the clearance and supporting thereon the free end portion of the power feeding cable.