Reduced graphene oxides (rGOs) with micropores were successfully obtained from a graphite oxide (GO) suspension in 2-propanol/water by electron beam irradiation at room temperature under ambient air conditions. During the radiolysis reaction, hydrated electrons (e− aq) were generated and acted as a reducing agent for the reduction of GO. The physico-chemical properties, such as disorder degree, oxygen content, specific surface area, pore structure, and sheet resistance of the rGOs were systematically controlled by adjusting the electron beam irradiation dose (50∼360kGy). Especially, higher irradiation dose reduced the oxygen content, increased the specific surface area, and increased the number of micropores of rGO, which are important factors for supercapacitor performance. In order to investigate the electrochemical performance of the rGOs, electrochemical measurements were performed with a three-electrode system in 6.0M KOH aqueous media. The highest capacitance of 206.8 F g−1 was achieved at a charge/discharge current density of 0.2Ag−1 in 6.0M KOH aqueous solution for a sample reduced by electron beam irradiation of 200kGy.