Herein, mesoporous carbon materials with different particle sizes were prepared using the direct templating method. To control particle size, the concentration of surfactant/silicate dissolved in aqueous solution was varied. According to a decrease in the concentration, a larger surface area and a smaller particle size were observed, whereas pore size and connectivity remained invariant. From the investigation of electric double-layer capacitor performance, specific capacitance was proportional to surface area. From electrochemical impedance spectroscopy analysis, a resistance relevant to pseudocapacitive faradaic reaction on electrode surface became larger, but a decrease in the total electrolyte resistance in pores was observed as a function of particle size decrease. This contradictory behavior of two resistances resulted in an existence of optimal particle size for the minimum equivalent series resistance …​