The present invention uses the principles of electrochemical ion absorption (charging) and ion desorption (discharge), and relates to a continuous flow-electrode system, a high-capacity energy storage system, and a water treatment method using the same, in which high-capacity electric energy is stored as electrode materials of a slurry phase and electrolytes simultaneously flow in a successive manner within a fine flow channel structure formed on an electrode. More specifically, the present invention relates to a continuous flow-electrode system, an energy storage system, and a water treatment method, wherein electrode active materials consecutively flow in a slurry state whereby a high capacity is easily obtained without enlarging or stacking electrodes.