Reoxidation of nickel catalyst in anode generally leads to deterioration of cell performance in solid oxide fuel cells (SOFCs). In this study, we aimed to clarify the correlation between microstructural and electrochemical characteristics during reduction-oxidation (redox) cycles for Ni-YSZ anode. Cell performance was deteriorated after the redox cycle because of the increase in polarization resistance of the anode. From the focused ion beam-scanning electron microscopy (FIB-SEM) analysis of Ni-YSZ anode, the continuous increase in surface area of nickel phase was observed after the each redox cycles, which indicated that the nickel particles became finer and more complicated shape. The length of triple phase boundary (TPB) in the Ni-YSZ anodes decreased continuously with the redox cycles. These results indicated that the increase in polarization resistance was caused by the decrease in the TPB length during the redox cycles for the Ni-YSZ anode.