In this study, characteristics of performance degradation caused by starved operation in one cell of a DMFC stack were investigated by comprehensive study based on the measurement of electrochemical behavior of cell and gas analysis of CO₂, and O₂ emissions in anode off gas. As a result, it was made clear that the degradation appears as decay of catalyzer activity only in anode, which is attributed to corrosion of carbon used as anodic catalyst support. This carbon corrosion reaction is predicted to be triggered by O₂ which is generated in the anodic reaction of water electrolysis caused in potential reversal. Since the degradation was suppressed by the use of carbon free catalyst such as Pt-Ru-black, it is estimated that use of much more tough anti-corrosive material than Ketjenblack which is used in this study is effective to mitigate performance decay caused by methanol starved operation.