Abstract: An object of the present invention is to provide a polydimethylsiloxane substrate to which a peptide having an affinity for polydimethylsiloxane (PDMS) is bound; a method for immobilizing a target protein on a polydimethylsiloxane substrate; a peptide having an affinity for PDMS; a polynucleotide encoding a peptide having an affinity for PDMS; and a vector using thereof. A polydimethylsiloxane substrate to which a peptide having an affinity for polydimethylsiloxane is bound, the peptide comprising the following peptide (1a) or (1b), or a fragment thereof: (1a) a peptide comprising an amino acid sequence represented by at least one member selected from the group consisting of SEQ ID NOs: 1 to 9; and (1b) a peptide comprising the amino acid sequence of (1a) in which one or more amino acids are deleted, substituted, and/or added, the peptide having an affinity for polydimethylsiloxane.