The purpose of the invention is to develop a silyl linker that can be efficiently introduced on a solid-phase support used for the synthesis of nucleic acid oligomers such as DNA. The present invention relates to a silyl linker for use in the solid-phase synthesis of nucleic acid, comprised of a compound of the general formula or its ester or salt: H—(R1)Si(R2)-(C6H4)—CONH-(A)-COOH  (I) wherein each of R1 and R2 is an alkyl or aryl group, and (A) represents a spacer moiety; a 3′-end nucleoside unit having said compound linked via an oxygen atom to the 3-position of a sugar of the nucleoside or its derivative, a solid-phase support having the 3′-end nucleoside unit, and a method for synthesis of nucleic acid oligomer with the use of said solid-phase support.