For the electric double layer capacitors(ELDC) made of phenol based activated carbon fiber(ACF) electrodes and aqueous electrolytes, the specific capacitance characteristics has been investigated with respect to different specific surface area of electrodes and different kinds of aqueous electrolytes. Throughout charge-discharge cell tests, it has been shown that larger surface area of electrodes and higher ion mobility of electrolytes have better specific capacitances. Also, it has been found that 1200℃ heat treatment of the electrode is effective to improve the specific capacitance over 140F/g.