A cell-penetrating peptide described in any of (A) to (D) below gives cellmembrane permeability and further transmucosal absorbability to aphysiologicallyactive substance:(A) a peptide having the amino acid sequence represented by SEQ ID NO: 1；(B) a peptide having an amino acid sequence which is the same as the aminoacid sequence represented by SEQ ID NO:1 except that one or several basicaminoacids are substituted, deleted, inserted and/or added, which peptide has cellmembrane permeability；(C) a peptide having an amino acid sequence which is the same as the aminoacid sequence represented by SEQ ID NO:1 except that 1 to 5 amino acids aresubstituted, deleted, inserted and/or added, which peptide has cell membranepermeability；(D) a peptide having: an amino acid sequence represented by the reversesequence of any of (A) to (C)； an amino acid sequence which is the same as theamino acid sequence represented by the reverse sequence of (A) except that oneorseveral basic amino acids are substituted, deleted, inserted and/or added； oran aminoacid sequence which is the same as the amino acid sequence represented by thereverse sequence of (A) except that 1 to 5 amino acids are substituted,deleted,inserted and/or added； which peptide has cell membrane permeability.
