Performance of supercapacitors is often influenced by their internal resistance since it causes unfavorable effects such as energy dissipation and delay of charge transport during charging/discharging. In the present study, we prepared monolithic metal nanowire array electrodes in aiming at suppressing the internal resistance of supercapacitors, and examined the influence of the defect structures present in the nanowire array electrodes. Performance of the supercapacitors was investigated by using galvanostatic charge/discharge measurement, cyclic voltammetry, and electrochemical impedance spectroscopy.