Removal of fluoride from geothermal water by electrodialysis (ED) was studied. ED operation was performed according to two methods. In the first method, before the ED operation, the pH of geothermal waters was adjusted to 7-7.5 by the addition of the HCl solution to prevent the precipitation of divalent salts in the concentrate compartment. In the second method, geothermal water was pretreated to precipitate the calcium ions. It was obtained that fluoride was effectively removed from geothermal water by electrodialysis using both of these pretreatment methods. However, it is preferable to use the first method because of its technically simple procedure and lower cost of chemicals used.