A fluoropolyether-containing polymer-modified silane having (1) is provided wherein Rf is a fluorooxyalkyl or fluorooxyalkylene-containing polymer residue, Y is a divalent to hexavalent hydrocarbon group, R is C1-C4 alkyl or phenyl, X is a hydrolyzable group, n is an integer of 1 to 3, m is an integer of 1 to 5, and α is 1 or 2. A surface treating agent comprising the silane or partial hydrolytic condensate thereof cures under mild conditions into a water/oil repellent layer having abrasion resistance, weatherability and low dynamic friction.