Abstract: An object of the present invention is to provide an antibody that can be stably supplied and can react with prostasin under non-denaturation and denaturation conditions, and an antigen peptide for preparation of the antibody. The present invention relates to a peptide consisting of the amino acid sequence shown in SEQ ID NO: 1 or a peptide consisting of an amino acid sequence that has a deletion, a substitution, or an addition of one or several amino acids with respect to the amino acid sequence shown in SEQ ID NO: 1 and having antigenicity of prostasin. Furthermore, the present invention relates to an antibody prepared using the peptide as an antigen.