The present invention relates to a water purifying device including: a cell unit consisting of a high purity ceramic for obtaining far infrared ray, and having a shape according to a kind of water tank, a ring-shaped Volta cell consisting of a non-ferrous metal being provided in the cell unit; and a lump unit being connected to the cell unit through a metal coil, and consisting of ceramic, a conductive lump consisting of a non-ferrous metal being provided in the lump unit. Accordingly, the water purifying device is easily installed in the water tank, for disinfecting bacteria, restricting generation of bacteria, removing odor, and facilitating growth of aquatic plants and fishes. As a result, a number of changing water in the water tank can be considerably reduced, to improve efficiency.