In this study, we propose a nanofluidic power generator inspired by an electrical eel to harness ion concentration gradient by reverse electrodialysis (RED). The key element for nanofluidic device, cation-exchange NCNM (CE-NCNM) and anion-exchange NCNM (AE-NCNM) constructed by self-assembled nanoparticles with hydroxyl and amine groups, respectively, enable high ionic current through 3-dimensional nanochannel networks for efficient power generation. The system performance is investigated by changing the number of serially stackable cells and intermembrane distance between cells.