The device for testing reverse osmosis membranes provides for the quick and efficient testing of the transport properties of reverse osmosis membranes at a fixed pressure over a fixed period of time. The device includes a first chamber adapted for receiving a volume of de-ionized water and a second chamber adapted for receiving a volume of brine. In use, a reverse osmosis membrane to be tested is clamped between the first and second chambers and a pressurized inert gas, such as gaseous nitrogen, is injected into the second chamber at known pressure to initiate reverse osmosis transport. The transport is carried out at the known pressure for a fixed period of time, after which the concentration of brine volume of water in the first chamber is measured.