One of the purposes of the present invention is to provide a polyether-modified siloxane having a good thickening property, in particular a good thickening property for an aqueous liquid. The present invention provides a polyether-modified siloxane represented by the following general formula (1):Sx-(CH2)aCOO—(C2H4O)n—(C3H6O)s—CO(CH2)a-Sx (1)wherein n is an integer of from 50 to 10000, s is an integer which meets the equation, 0<；=s<；=n/50, a is an integer of from 2 to 40, and Sx is, independently of each other, an organo(poly)siloxanyl group represented by the following formula (a) or (b):wherein R is, independently of each other, a hydrogen atom, a hydroxyl group, an alkoxyl group, or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, m is an integer of from 0 to 350, and m′ is an integer of from 0 to 348,wherein a ratio of a total molecular weight of the Sx-(CH2)aCO moieties to a molecular weight of the O(C2H4O)n(C3H6O)s moiety is 0.12 or smaller.
