A full-effect reverse osmosis membrane element includes a central tube and a reverse osmosis membrane assembly wound around the central tube. The reverse osmosis membrane assembly includes a pair of reverse osmosis membranes attached at front surfaces thereof and wound around the central tube. A water feed channel has a water inlet formed at front edges of the reverse osmosis membranes and a water outlet formed at rear edges of the reverse osmosis membranes. A water division structure is arranged in the water feed channel, and includes a first water division band forming a preset space with the central tube when the reverse osmosis membranes are in an unfolded state. The first water division band divides the water feed channel into a first flow channel having a gradually decreasing cross-section and a second flow channel in communication with the first flow channel.