Object of the present invention is to develop an artificial synthesis system of various peptides having an azole derivative structure and develop a library of such peptides. The present invention provides a method of producing a peptide having, in the backbone thereof, an azole derivative structure comprising the step of: synthesizing a substrate peptide of an azoline structure introducing enzyme having, in the modified region thereof, at least any one of the following amino acids, [in any of the compounds, X1 represents a group selected from the group consisting of SH, OH, NH2, SR1, OR1, NHR1, and N3 (R1 represents a protecting group), X2 represents an easily eliminable group; and X3 represents hydrogen or a substituted or unsubstituted alkyl or aryl group having from 1 to 10 carbon atoms]; reacting the substrate peptide with an azoline structure introducing enzyme to obtain a peptide having an azoline derivative structure; and converting the azoline derivative structure of the resulting peptide into an azole derivative structure by inducing an HX2 elimination reaction of X2 group.