The La0.5Sr0.5MnO3 (SLM)-8 mol % yttria stabilized cubic zirconia (YSZ) composite film electrodes were prepared by co-sputtering SLM and YSZ under an argon and oxygen mixed atmosphere. The electrical conductivity and cathodic overpotential of these composite films were examined. The cathodic overpotential of SLM was decreased by co-sputtering SLM and YSZ. The addition of YSZ to SLM diminished the grain growth of SLM by annealing at a high temperature.