Sulfonated poly(ether ether ketone)s (sPEEKs) are prepared and studied as a membrane and cathode binder for direct methanol fuel cell (DMFC). The effect of sPEEK content as a binder in the cathodic catalyst layer on the performance of the cell with the given anode is investigated. An electrochemically active surface area (EAS) and bulk ionic conduction of the electrode are investigated as a function of sPEEK binder content in the cathode. EAS decreased with higher binder content, and bulk ionic conduction of the electrode decreased with lower binder content in the cathode. Thus, it is necessary to optimize the binder content in the cathode. In this study, the unit cell with a cathode containing 5wt.% sPEEK binder showed the best cell performance due to rather high EAS and proton conductivity in the cathode.