Abstract: An apparatus for treating waste water including: a first flocculation tank to which a first flocculant is provided to produce a first flocculated material in which fluorine in waste water introduced from a waste water storage part is coagulated; a second flocculation tank to which a second flocculant and carbon dioxide are provided to produce a second flocculated material in which the first flocculated material and residual fluorine in first outflow water introduced from the first flocculation tank are flocculated; a third flocculation tank to which a third flocculant is provided to produce a third flocculated material in which the first flocculated material and the second flocculated material in second outflow water introduced from the second flocculation tank are flocculated; a first sedimentation tank in which third outflow water introduced from the third flocculation tank is solid-liquid separated into first sludge containing the third flocculated material and first supernatant water; a nitrification tank