PURPOSE: To supply to an ethylene glycol system by using a crude ethylene glycol flow having a specified pH value by the addition of acid, to purify the crude ethylene glycol flow, and to recover polyester-class high purity ethylene glycol from the ethylene glycol distillation system.

CONSTITUTION: Crude ethylene glycol which has a standard boiling point not exceeding that of ethylene glycol and contains at least one kind of component such as dialkyl oxalate and alkyl glycolate which can form an ultraviolet absorbing substance in the presence of ethylene glycol is added with an acid such as phosphoric acid to make a crude ethylene glycol flow which has a measured pH value lower than 7.5, preferably 4.0-7.5 to be supplied to an ethylene glycol distillation system having a fractional distillation zone equipped with an upper part, a lower part, and an intermediate part to be purified, and high purity ethylene glycol applicable to polyester fiber production, etc., is recovered from the lower part of the zone.