One of the problems related to water consumption in Moldova, distinguished by the low coefficient of stream frequency under the high density of population, is the necessity of water purification from the increased toxic substances’ content, particularly from fluorine. For water defluoridation we have used the electrodialysis method related to ionized substances’ migration through the semipermeable membranes under electric power action. It refers to the ecologically appropriate resource- and powe-saving processes. There are designed produced 3, 5, 7-chamber electrodialyzers equipped with ion-selective membranes MA 40 and MK 40. Each membrane, as well as the electrodialyzer frame had the necessary quantity of distributive orifices, which allowed creating the three independent, immiscible fluids’ flow inside the apparatus: the electrolyte, cleansing agent and working fluid. The regularity of fluorine ions’ removal is studied using electrodialysis from the pattern fluid (with the fluorine content up to 250 mg/dm3) and from the water of two sources – from Orhei and Straseni districts with the initial fluorine content 2 and 8 mg/dm3, respectively. The influence on the level of fluorine ions’ removal from water by electrodialysis method of some electric, diffusive and hydrodynamic factors is studied: a) voltage gradient between electrodes; b) distance between membranes and their distribution character with regard to electrodes; c) ion-selective membranes’ type (cation-exchange, anion-exchange); d) duration of water stay in intermembranous space; e) electrolytes concentration (sulphuric acid, solution of sodium sulphate); f) cleansing agent nature (tap water, citric acid, solution of sodium sulphate); g) throughput rate of working fluid and cleansing agent in the intermembranous space. It has been established that the greatest influence on the electrodialysis efficiency of water purification from fluorine ions have the first four factors. The optimal conditions of toxic fluorine ions’ removal using electrodialysis have been found, permitting to obtain the purified water with fluorine content under the Maximum Permissible Concentration norms. The advantages of electrodialysis method are shown as compared with the sorption methods of water purification from fluorine ions. It has been established that the power inputs for 1 m3 water purification with fluorine content about the 10 mg/dm3 by electrodialysis method do not exceed 5 kW per hour.