To provide a method and apparatus for detoxicating halogen compound-containing oil, by which purified oil can be effectively obtained by effectively removing solid impurity in the dehaloganated oil with small amount of energy.

The treating apparatus 1 for detoxicating the halogen compound-containing oil includes: a reaction tank 15 dechlorinating PCB in the oil to be treated with a metal sodium and obtaining treated oil; a decomposition confirming tank 17 confirming PCB concentration in the treated oil; a flocculation generating tank 19 adding sludge and water into the treated oil as flocculant and flocculating the solid impurity and the sludge contained in the treated oil as seed crystals; a precipitating tank 21 precipitating and separating flocculated solid impurity and recovering the dehalogenated oil not containing the solid impurity; a condensing tank 23 further condensing the flocculated solid impurity discharged from the precipitating tank 21; and a seed crystal-returning line 28 returning a part of the sludge discharged from the condensing tank 23 to the flocculation generating tank 19.