PURPOSE: To regenerate a strong basic anion exchange regin with good efficiency, by feeding water to the ion exchange resin layer having deteriorated ion exchanging power, and agitating said resin layer then feeding the water further from the lower part while feeding pressurized water from the upper part then backwashing the resin.

CONSTITUTION: Crude hydrochloric acid contg. iron ions is introduced from an original liquid tank 6 through a diffusion pipe 3 into an ion exchange column 1 provided with a Cl type strongly basic anion exchange resin layer 2, and is passed through the layer 2 whereby the exchange of Cl ions with iron ions is effected. The refined hydrochloric acid is removed from an outflow pipe 9. The regeneration of the layer 2 is accomplished by discharging the residual hydrochloric acid from the inside of the column 1, then feeding industrial water and pressurized air to stir the layer 2, admitting the industrial water into the column 1 from the lower part thereof while introducing pressured water or pressurized air from the upper part thereof, and discharging the waste water of regeneration, the pressurized water, etc. from the above-mentioned pipe 3. The water is then passed from the lower to upper part of the column 1 to backwash the resin layer 2, whereby said layer is regenerated.