PROBLEM TO BE SOLVED: To provide a disinfectant demonstrating sufficient bactericidal effect without corroding an RO membrane material, without a deteriorating in the quality of pure water and ultrapure water obtained by treatment and further, in the RO membrane treatment process of making pure water and ultrapure water and the like. SOLUTION: A reverse osmosis membrane treatment agent contains a bactericidal agent such as a halo cyanoacetamide compound and an alcoholic or glycolic organic solvent containing a specific structure 1 or structure 2 hardly capable of permeating the RO membrane. A reverse osmosis membrane treatment method using the above agent is also disclosed. COPYRIGHT: (C)2009,JPO&INPIT
