The present invention relates that peptides having an ability to bind to a cell or penetrate into a cell are selectively enriched from a random peptide library with a diversity of not less than one hundred millions of peptides using a phage surface display technique, and cytoplasmic transfer is evaluated by using protein synthesis inhibition as an indicator by adding into a cell, a fusion body of the selectively enriched peptide and a protein synthesis inhibitory factor (PSIF) that can not solely penetrate into the cell.
