A polyamide skin layer is formed on a porous support by reacting an
aromatic compound having at least two reactive amino groups with a
polyfunctional acid halide compound having at least two reactive acid
halide groups. Then, the polyamide skin layer is treated with a free
chlorine aqueous solution containing bromine compound. The resultant
composite reverse osmosis membrane has a high rejection for substances
that are not ionized at the pH range where the membrane is normally used.
