An object of the present invention is to provide an oligosaccharide chain added GLP-1 peptide that has higher stability in blood than that of GLP-1 and, preferably, exhibits higher activity of controlling blood-sugar levels than that of GLP-1. The present invention provides an oligosaccharide chain added GLP-1 peptide having GLP-1 activity, wherein at least two amino acids are each substituted with an oligosaccharide chain added amino acid, in (a) GLP-1； (b) a peptide having the amino acid sequence of GLP-1 with deletion, substitution or addition of one or several amino acids； or (c) a GLP-1 analog. The present invention also provides an oligosaccharide chain added GLP-1 peptide having GLP-1 activity, wherein at least one amino acid is substituted with an oligosaccharide chain added amino acid, in the (a), (b) or (c) and the oligosaccharide chain is an oligosaccharide chain comprising oligo hyaluronic acid. In the oligosaccharide chain added amino acid, the oligosaccharide chain may be linked to the amino acid via a linker.
