A new ribosome display system was applied for the in vitro selection of a metal-binding motif from an artificial peptide library. The display system consisted of an mRNA-associating protein, a ribosome, and mRNA. The protein part of this display system was designed to provide a random peptide library and to stabilize the ribosome display. The random peptide library was newly designed to isolate stable metal-binding motifs. We employed the system for in vitro selection and found several new proteins and peptides that bind Co(II)-immobilized resin and Co(II)complex, respectively. This newly developed system can be conveniently applied to the in vitro selection of peptide aptamers.