The present invention provides methods which enables synthesis of various sugar chains and products obtained by the same. More specifically, the present invention provides protected sugar chain compounds represented by the formula (I) below: [wherein R1 and R2 are the same or different and each is a linear or branched sugar chain, S1 is any sugar residue, SA and SB are the same or different sugar residues, L is a bond or a linear sugar chain, X is absent, or, if present, represents certain group, the sugar residues SA and SB are cleaved by different exoglycosidases, respectively] and libraries thereof, and methods of producing the same; methods of producing a sugar chain compound, which comprises treating the sugar chain compound or library with glycosidase, and glycosidase decomposition products obtained by the same; intermediates for the synthesis of protected sugar chain compounds; reagents and kits; and the like.