Drainage water containing organofluorine compounds is introduced into a micro-nano-babble generation tank (1) wherein microorganisms from a microorganism tank (61), a micro-nano bubble auxiliary agent from an auxiliary agent tank (50), a nutrient from a nutrient tank (52) and micro-nano-babbles generated by a micro-nano babble generator (23) are added to the drainage water so as to produce treatment water. The treatment water is fed from the micro-nano babble generation tank (1) to an active carbon tower (4) wherein the organofluorine compounds contained in the treatment water are decomposed with the microorganisms.