The purpose of the present invention is to provide: a peptide having an affinity for silicon nitride; a polynucleotide encoding the peptide; an expression vector for expressing the peptide having an affinity for silicon nitride; an expression vector for expressing a peptide fusion protein that comprises the peptide having an affinity for silicon nitride and a target protein; a transformant obtained by introducing the expression vector into a host cell; a peptide fusion protein obtained from the transformant; a silicon nitride substrate to which a peptide having an affinity for silicon nitride has been bonded; a method for immobilizing a target protein to a silicon nitride substrate; a composition for immobilizing a target protein to a silicon nitride substrate, the composition comprising a peptide having an affinity for silicon nitride; and a linker for immobilizing a target protein to a silicon nitride substrate, the linker comprising a peptide having an affinity for silicon nitride. The invention involves a
