A peptide nanofiber having conductivity is provided. A conductive peptide nanofiber which includes a nanofiber formed through a manner of self-assembly of a peptide that has a nanofiber-forming ability and consists of an amino acid sequence of Xaa-Phe-Ile-Val-Ile-Phe-Xaa (SEQ ID NO: 1, wherein N-terminal Xaa is an arbitrary amino acid residue Xaa.sub.1; C-terminal Xaa is an arbitrary amino acid residue Xaa.sub.2; and Xaa.sub.1 and Xaa.sub.2 are an amino acid having an acidic side chain, an amino acid having a basic side chain, or an amino acid having a side chain with polarity according as acidity and basicity) or a derivative of the peptide and a conductive substance added thereto, the aforementioned conductive substance being added to an amino group of the peptide or the derivative.