An apparatus for waste water treatment, wherein fluorine contained in waste water is treated into a fluoride through a chemical reaction and sludge containing the fluoride is thickened and dehydrated into a sludge cake, has first and second tanks each packed with calcium carbonate mineral. In the first tank, waster water containing fluorine is agitated by air discharged from an air diffuser and caused to react with the calcium carbonate mineral. Through this reaction of the waste water with the calcium carbonate mineral and action of microorganisms on the surface of the calcium carbonate mineral, a pH value and a fluorine concentration of the waste water is adjusted till the pH value and the fluorine concentration fall within their respective predetermined ranges. In the second tank, an aluminum agent is added to the waste water coming from the first tank while the waste water being agitated so that the pH value and the fluorine concentration of the waste water are further adjusted through a chemical reaction of the fluorine with the calcium carbonate mineral and aluminum agent and action of microorganisms propagating on the surface of the mineral so as to fall within their respective target ranges.