The present invention is a water processing method comprising the steps of separating boron-containing water in a reverse osmosis membrane module to provide a permeated water and subjecting a part of the obtained permeated water to boron removal using an adsorbent, wherein the water subjected to the boron removal is mixed with the water not subjected to the boron removal of the permeated water to provide a mixed water. The present invention provides economic water processing method and apparatus that remove the boron from boron-containing water.