The RuO2/carbon fiber nanocomposite webs were prepared by a co-electrospinning technique in order to use as electrodes of supercapacitor. At first, the PAN-RuO2 fiber web was prepared by an electrospinning technique to use the mixed solution of both polyacrylonitrile (PAN) in N,N-dimethylformamide (DMF) and 10 to 20 wt.% ruthenium oxide hydrate (RuO2). The electrospun PAN-RuO2 fiber web was stabilized at 280C, and then carbon-RuO2 nanofiber web was synthesized by activating at 800 C in the steam atmosphere. The specific capacitance is increased with increasing RuO2 contents. But the specific capacitance is decreased at 20 wt.% RuO2/carbon fiber nanofiber. The specific capacitance of 10 wt.% RuO2/carbon, 15 wt.% RuO2/carbon, 20 wt.% RuO2 /carbon and activated carbon nanofiber or nanofiber composite electrode are 365, 461, 390, 140 F/g, respectively at 1mA/Cm2. In the case of RuO2 addition, the specific capacitance is improved due to the synergic effect of pseudocapacitance.