A novel nanocarbon composite structure is provided having trapped ruthenium oxide. By using Ketjen black, and through chemical-mechanical effect utilizing an ultracentrifugal reaction field, both the specific surface area of ruthenium oxide and space of electrode material are expanded to have nanoparticles of ruthenium oxide highly dispersed in a graphene layer. This nanocarbon composite structure having trapped ruthenium oxide exhibits high electrochemical activity and is suitable for use as an electrical energy storing device, such as a large-capacity capacitor.