The present invention provides a perfluoro(poly)ether group containing silane compound which is able to form a layer having water-repellency, oil-repellency and antifouling property as well as high friction durability, and represented by the formula (1a) or the formula (1b): €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒA - Rf - X - SiQ k Y 3-k –ª–ª–ª€ƒ€ƒ€ƒ€ƒ€ƒ(1a) €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒY 3 - k Q k Si-X-Rf-X- SiQ k Y 3-k –ª–ª–ª€ƒ€ƒ€ƒ€ƒ€ƒ(1b) wherein A represents a C 1-16 alkyl which may be substituted by one or more fluorine atoms; Rf represents -(OC 9 F 8 ) a -(OC 3 F 6 ) b -(OC 2 F 4 ) c -(OCF 2 ) d -wherein a, b, c and d are each independently an integer of 0 or more and 200 or less, the sum of a, b, c and d is 1 or more and the occurrence order of the respective repeating units in parentheses with the subscript a, b, c or d is not limited in the formula; X represents a divalent organic group; Y represents, each independently at each occurrence, a hydroxyl group, a hydrolyzable group, or a hydrocarbon group; Q represents, each independently at each occurrence,-Z-SiR 1 n R 2 3 - n ; Z represents, each independently at each occurrence, a divalent organic group: with the proviso that Z is not a group which forms a siloxane bond together with a Si atom present in the end of a molecular backbone of the formula (1a) or the formula (1b), R 1 represents, each independently at each occurrence, a hydroxyl group or a hydrolyzable group; R 2 represents, each independently at each occurrence, a C 1-22 alkyl group or Q'; Q' has the same definition as that of Q; n is, each independently in each Q and Q', an integer selected from 0-3, and the total sum of n one or more; in Q, the number of Si atoms which are straightly linked via the Z group is up to five; k is an integer each independently selected from 1-3.