A method for making reverse osmosis permeate water and mineral water from deep seawater includes the steps of: a) sand-filtering or ultra-filtering the deep seawater; b) conducting a first nano-filtering step to nano-filter the deep seawater after the step a) to obtain first nano-filtration permeate water and first nano-filtration concentrated water; c) filtering the first nano-filtration permeate water using a reverse osmosis apparatus to obtain reverse osmosis permeate water and reverse osmosis concentrated water; and d) treating the first nano-filtration concentrated water by electrodialysis to obtain anion-rich water, cation-rich water, and mineral water.