To provide a method for treating fluorine-containing waste water and a device therefor by which the concentration of fluorine and the concentration of calcium in treatment water can be indirectly controlled, a high fluorine removing performance can be obtained, and the utilizing efficiency of calcium carbonate can be improved and also the amount of sludge can be reduced.

The treatment method includes: a treatment step A where, regarding fluorine-containing waste water, the pH of a hydrofluoric acid solution in which a fluorine ion concentration is wholly derived from hydrofluoric acid and also other acid is not comprised is calculated, the pH of the fluorine-containing waste water is regulated in such a manner that the difference pH of the fluorine-containing waste water to the calculated pH is controlled to the range of -0.5 to +1.0, and the fluorine-containing waste water is passed through a calcium carbonate packed column 13; a flocculation-separation step B where a calcium compound is added to the fluorine-containing waste water after the calcium carbonate packed column treatment stage A, so as to perform treatment in such a manner that the concentration of fluorine is controlled to 20 mg/L; and a crystallization step C where, in a phosphoric acid based chemical and a calcium compound, at least the phosphoric acid based chemical is added to the fluorine-containing waste water after the flocculation-separation stage, and water is passed through a crystallization column 16.