PURPOSE: To provide a method for regenerating an anionic resin or a cationic resin to reuse it for water purification.

CONSTITUTION: This method comprises following processes: a process to feed an anion particle to be regenerated to a first container 10, a process to add a mixture comprising non-regenerated anion particles and cation particles into the first container, a process to separate each cation particle and anion particle into a second container 12 and a third container 64, where the cation particles and the anion particles are formed as a mixture in a boundary between anion particles and cation particles, a process for re-generating the anion particles by impregnating them into a sodium hydroxide, a process to mix again the regenerated anion particles with non-regenerated cation particles, a process to return non-regenerated cation particles into the second container by separating non-regenerated cation particles again, a process to regenerate cation particles by immersing them into a hydrochloric acid or a sulfuric acid, and a process to transfer the re-generated anion particles of an amount normally used together with the cation particles of a given volume into a fourth container.