PROBLEM TO BE SOLVED: To provide a novel substance having excellent neuraminidase inhibiting activity and/or tyrosinase inhibiting activity.SOLUTION: A mimosine derivative is represented by general formula (1). Here, Xto Xindependently show amino acid residues selected from a group comprising a tyrosine (Tyr), a tryptophan (Trp), a phenylalanine (Phe), a glycine (Gln), a glutamine (Gln) a valine (Val), and a histidine (His).