Chemical mixing of carbon and amorphous hydrous manganese oxide (a-MnO2.nH(2)O) particles as an active material for electrochemical pseudocapacitor was proposed to increase the efficiency of added carbon as a conducting agent to expand the active site area on the surface of a-MnO2.nH(2)O particle. Instead of physically mixing the conducting carbon and active material using a mortar or ballmilling, added carbon was mixed during synthesis reaction of the active material. The chemical mixing proposed in this study was effective for increasing specific capacitance and improving electrochemical properties as an electrochemical pseudocapacitor to show closer ideal capacitor behavior in high power mode compared with physically mixed electrode.