An electrochemical cell for the treatment of water and/or water solutions comprises an internal electrode having a middle section and a pin-end at each end thereof, the diameter of each pin-end being not more than 0.75 of the diameter of the middle section; an external electrode mounted around the internal electrode; and a coaxial ceramic diaphragm mounted in a separate inter-electrode space in an electrode chamber of the cell. The external electrode is mounted in lower and upper dielectric bushings. Both the internal electrode and the external electrode are connected with positive and negative poles of a power supply. The cell further includes an upper dielectric collector head and a lower dielectric collector head which each have an axial channel; each collector head being installed in the bushing slots and adapted for turning therein. The diaphragm being fastened by elastic gaskets mounted in the slots of the bushings. The diameter of the middle section of the internal electrode being defined by the formula:2M