Provided are a peptide gel with practically sufficient mechanical strength and a self-assembling peptide capable of forming the peptide gel. The self-assembling peptide is formed of the following amino acid sequence: a 1 b 1 c 1 b 2 a 2 b 3 db 4 a 3 b 5 c 2 b 6 a 4 where: a 1 to a 4 each represent a basic amino acid residue； b 1 to b 6 each represent an uncharged polar amino acid residue and/or a hydrophobic amino acid residue, provided that at least five thereof each represent a hydrophobic amino acid residue； c 1 and c 2 each represent an acidic amino acid residue； and d represents a hydrophobic amino acid residue.
