The differences in the destruction mode of anode-supported solid oxide fuel cells (SOFCs) as a result of small and large amounts of oxidation were investigated. The cells were oxidized by O2- ions and rereduced by H-2 gas (redox cycle). When 0.6% of Ni in the anode was oxidized, its microstructure near the electrolyte changed. Although this microstructural change in the anode by early redox cycles did not cause performance degradation, minor damage accumulated as the redox cycles increased. An increase in the microcracks in the anode led to partial delamination of the electrolyte, which finally resulted in a crack in the electrolyte. In contrast, when 31% of Ni in the anode was oxidized, a crack in the electrolyte was suddenly caused by two redox cycles. Because the electrolyte did not delaminate by a few redox cycles, the anode strain caused the electrolyte to crack, as reported by many researchers.