Substrate-type solid oxide fuel cells (SOFCs) can reduce the operating temperature of SOFCs to enable alloys to be used as separators. When chromium-forming alloys are used as the separators, however, the performance of SOFC cathodes degrades rapidly. The degradation of a porous La0.6Sr0.4MnO3+delta (LSM)/YSZ electrode in contact with the alloy current-collector has been investigated using the frequency dispersion diagram of the complex impedance of the electrode. The equivalent circuit analysis based on a Randles-type equivalent circuit made clear that the Cr2O3 deposition at the interface between the LSM and the YSZ electrolyte causes an increase in both diffusion and charge-transfer resistances.