The present invention relates to a polyether derivative represented by the following general formula (I): ##STR00001## wherein X.sup.1 represents --CO-- or --SO.sub.2--; Ar.sup.1 represents unsubstituted arylene, or arylene substituted with a halogen atom, or an alkyl, alkenyl, alkynyl, alkoxy, alkoxycarbonyl aryloxycarbonyl or cyano group; L represents alkylene; m is 1 or 2; A represents --X.sup.2--Ar.sup.2--(NH.sub.2).sub.1, a hydrogen atom, or an alkyl, aryl or acyl group, wherein X.sup.2, Ar.sup.2 and l have the same meanings as the above-mentioned X.sup.1, Ar.sup.1 and m, respectively; and n is the average addition mole number of the polyether group, and is a numerical value of 10 to 500.