PURPOSE: To provide a anti-freezing solution-recycling system of high efficiency which can minimize the time loss needed for cleaning and exchanging the membrane because the membrane can be cleaned in parallel with the recycling treatment of the antifreezing solution.

CONSTITUTION: In this recycling system, a plurality of reverse osmotic membranes 5 are used as a means for recycling a used antifreezing solution 9 containing (A) ethylene glycol, (B) additives, (C) oxidized products of component A, (D) deteriorated products of component B, (E) dissolved metal components and (F) insoluble solids, while the other reverse osmotic membranes 5 are cleaned, preferably by using a detergent-circulating pump 12 to circulate the detergent in a tank 11 for detergent. For example, relatively large component F is removed from the antifreezing solution 9 using filters 3a, 3b, then water and components A-E are separated with membrane 5a, further fed to an ion-exchange resin 6 to give a treated solution 10.