To economically regenerate a cooling liquid by combining the cation trapping process bringing the deteriorated cooling liquid into contact with a chelate resin and the anion trapping process bringing it into contact with a weak basic anion exchange resin and a strong basic anion exchange resin in sequence for the ion removing process.

A deteriorated engine cooling liquid is fed to an adsorption tank 4 filled with an activated carbon and a cation separator 5 filled with a chelate resin in sequence via a filter 3 by a liquid feed pump 2 from a stock solution tank 1, then it is guided into an anion separator 6 filled with a weak basic anion exchange resin layer 61 and a strong basic anion exchange resin layer 62 for an ion removing process. The refined engine cooling liquid is added with a necessary additive and is fed to a regenerating liquid tank 8 for generating a regenerated engine cooling liquid. The deterioration of the ion exchange resin used to recover and refine the deteriorated engine cooling liquid can be suppressed, and the engine cooling liquid can be refined and regenerated very economically.