Activated carbons (AC) powder was coated onto Al current collectors with different thickness (∼30 and ∼80μm) for use as electrodes of supercapacitors. The relationship between the electrode thickness and the specific capacitance of the supercapacitor cells using a non-aqueous electrolyte was investigated under different charge–discharge current density and for charge–discharge cycling at constant current density. Two types of microporous AC powders of which specific surface areas were 1454 and 2587m2/g were deposited using a binary binder composed of styrene-butadiene rubber and sodium carboxymethyl cellulose. The rate stability of the specific capacitance was shown to be independent of the electrode thickness, and thinner electrodes could maintain higher specific capacitance regardless of the AC type. Thicker electrodes allowed a larger increase in equivalent series resistance with cycling, decreasing the voltage allocated to the formation of the electrical double-layer and thus reducing the specific capacitance. Microscopic surface observation showed that the thicker electrodes exhibited voids resulting from reduced adhesion among AC particles. The reduced adhesion and the electrolyte decomposition in the thicker electrodes were likely to be connected to their performance deterioration.