PURPOSE: To easily treat waste water contg. org. solvents in the stage of treating the said water by subjecting the waste water to air stripping to drive out the org. solvents in the waste water to the air side and introducing such gas into a combustion furnace normally installed to a drying furnace thereby burning the gas.

CONSTITUTION: The waste water W1 of electrodeposition painting and waste water W2 of washing in electrodeposition painting lines 1W4 consisting of electrodeposition painting, washing and drying stages are aerated in a tank 7 so that the org. solvents contained in the waste water are evaporated by stripping from the waste water. After mists are removed from the air G2 contg. such org. solvents by a mist separator 9, the gas is conduced to the combustion device 6 for treating the waste gas of the drying furnace so that the stripped org. solvents are burned simultaneously with the waste gas G3 of the drying furnace. As a result, the need for the org. solvent treatment on the discharge side in the conventional practice is eliminated and the waste water treatment is made easy; in addition, the normally installed device is effectively usable as it is for treating the gas subjected to the air stripping.