The present invention relates to 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 relates to 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:(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.
