The performance of yeast-based microbial fuel cells (MFCs) and the growth pattern of yeast were evaluated with the optimization of dead zone within carbon felt (CF) electrode. Yeast cells were grown onto the different CFs that have 1 to 4mm thicknesses, while optical and electrochemical evaluations were implemented to determine the optimal growth pattern of yeast and to elucidate a relationship between the growth pattern of yeast and the performance of MFC. According to the evaluations, biofilm consisting of high-density yeast cells is formed in the upper 1mm height of CF electrode. As the height goes down, density of yeast cells is reduced to less than half of the upper biofilm, and by calculating the growth rate of yeast cells per CF volume, it is recognized that the coverage of biocatalyst including yeast cell increases from 0.191 to 0.406 μmol/cm3 with decreasing CF thickness. Then, the performance of MFCs using biocatalysts including yeast cells grown on different thick CFs is measured to investigate how the growth pattern of yeast cells affects the performance of MFCs. Results show their maximum power density (MPD) increases linearly as the area that yeast cells are filled increases, and when CF thickness is 1mm, MPD reaches 417.13 W/m3.