As an activation procedure, in this study, the oxidation treatment of needle cokes with a dilute nitric acid and sodium chlorate (NaClO3), combined with heat treatment, was attempted. The structures of acid-treated and pyrolyzed coke were examined with XRD, FESEM, elemental analyzer, BET, and Raman spectroscopy. The behavior of double layer capacitance was investigated with the analysis of charge and discharge. The structure of needle coke treated with acid was revealed to a single phase of (001) diffraction peak after 24 h. On the other hand, thecoke oxidized by heat treatment was reduced to a graphite structure of (002) at 300 ℃. The distorted graphene layer structure, derived from the process of oxidation and reduction of the inter-layer, makes the pores by the electric field activation at the first charge, and generates the double layer capacitance from the second charge. The cell using pyrolyzed coke with 24 h acid treatment and 300 ℃ heat treatment exhibited the maximum capacitance per weight and volume of 33 F/g and 30 F/mL at the two-electrode system in the potential range of 0∼2.5 V.