To provide an N-acetylglucosamine-bound opioid peptide derivative expected to have improved stability to heat, pH and enzymic digestion, and possibility of passage or the like through blood-brain barrier.

The N-acetylglucosamine (GlcNac)-bound opioid peptide derivative has the GlcNac bound by glycoside to at least one hydroxy group at a side chain selected from hydroxy groups of the side chains of L-tyrosine (Tyr) at 1-position, D-serine (D-Ser) at 2-position and L-threonine (Thr) at 6-position in L-tyrosyl-D-serly-L-glycyl-L-phenylalanyl-L-leucyl-L-threonine (H-Tyr-D-Ser- Gly-Phe-Leu-Thr-OH).