PROBLEM TO BE SOLVED: To remove organic substances and 1,4-dioxane contained in waste water at a low cost.SOLUTION: There is provided a device for treating 1,4-dioxane-containing waste water which comprises: an anaerobic tank 1 for removing organic substances contained in 1,4-dioxane-containing waste water by anaerobic biological treatment; and an aerobic tank 3 for removing residual organic substances and 1,4-dioxane contained in treated water by aerobic biological treatment. In the anaerobic tank 1, for example, an upflow anaerobic sludge blanket method or an expanded granule sludge blanket method is applied. In the aerobic tank 3, for example, a long time aeration method or a membrane separation activated sludge method is applied. Methane gas generated in the anaerobic tank 1 is, for example, used as a fuel of a heat source 6 for heating the anaerobic tank 1.
