The direct methanol fuel cell is one of the most promising candidates of the next-generation power sources for small electric appliances. However, there still remain some issues, one of which is regarding carbon dioxide bubbles generated in the anode channel. They tend to cover the gas diffusion layer (GDL) surface, obstruct the reaction and deteriorate the overall fuel cell performance. Therefore, it is important to clarify the flow mechanisms of the gas-liquid two-phase flow of methanol solution. In this study, the influence of wettability of the anode channel walls on the fuel cell performance was investigated along with flow visualization and pressure measurements using a special experimental setup. The results showed that a higher and more stable output voltage was obtained in the fuel cell with hydrophobic channel walls. The results also showed that CO₂ bubbles tended to detach from the GDL surface, merge and attach to the hydrophobic channel walls, which probably led to facilitate fuel supply and CO₂ gas emission.