To realize an efficient method excellent in productivity by using water or alcohol for cleaning a saponified ethylene/vinyl acetate copolymer containing water or alcohol while blowing in an acidic gas.

Water or aqueous alcohol is added to a saponified ethylene/vinyl acetate copolymer containing water or aqueous alcohol to give a total of 1.5-20 times the weight of the saponified copolymer. The mixture is agitated at 10-40°C for 1-10 hr while an acidic gas such as carbon dioxide is blown in, thus removing impurities such as sodium acetate. The mixture is then dried to a water content of 0.001-2 wt.% and if necessary, blended with a plasticizer, a heat stabilizer, an ultraviolet absorber, an antioxidant, an anti-gelling agent, a filler, etc. The saponified ethylene/vinyl acetate copolymer preferably comprises one having an ethylene content of 20-60 mol% and a degree of saponification of 90 mol% or higher. The anti-gelling agent used comprises, e.g. a hydrotalcite compound, while a hindered phenol base or hindered amine base heat stabilizer or the like is used.