A nanoporous nickel (Ni) substrate was successfully prepared by selective dissolution of copper (Cu) from a Ni–Cu alloy layer. It was noted that both the Cu etching and the Ni/Cu codeposition processes could be performed in the same solution. Afterwards, anodic deposition was carried out to disperse fibrous manganese (Mn) oxide onto the nanoporous Ni substrate. As a result, a novel oxide electrode with a high-porosity structure was fabricated by the totally electrochemical procedure, which is very simple and efficient. Pseudocapacitive performance of this oxide electrode was evaluated by cyclic voltammetry in 0.1M Na2SO4 solution. The data indicated that specific capacitance of the Mn oxide was as high as 502Fg−1, which was 85% higher than that deposited on a flat electrode. Capacitance retained ratio after 500 charge–discharge cycles of the Mn oxide was also significantly improved from 75 to 93% due to the use of the nanoporous substrate.