A peptide according to the present invention is selected from the group consisting of: (a) a peptide having the amino acid sequence represented by SEQ ID NO: 1; (b) a peptide having a modified amino acid sequence of the amino acid sequence described in (a) above, in which one or more amino acid residues are deleted, substituted, inserted or added, and having cell death-preventing activity and/or cell growth-promoting activity; and (c) a peptide which has an amino acid sequence having at least 80% homology with the peptide consisting of the amino acid sequence described in (a) above and has cell death-preventing activity and/or cell growth-promoting activity. The peptide has cell death-preventing activity and/or cell growth-promoting activity, is highly safe, and can be produced without difficulty. The peptide is useful as a culture supplement or as an effective component for a cell culture medium.