The purpose of the present invention is to provide an antibody against fibroblast growth factor 23. The antibody is obtained by immunizing an animal with a polypeptide which comprises an amino acid sequence represented by SEQ ID NO: 1, or an amino acid sequence derived from the amino acid sequence represented by SEQ ID NO: 1 by deletion, substitution, or addition of 1 or several amino acids, and has fibroblast growth factor-23 activity and activity to control phosphate metabolism or vitamin D metabolism, and is shown by the following (a), (b), or (c): (a) an antibody, which recognizes an amino acid sequence between the 180 and the 194, or the 237 and the 251<st> amino acid residues represented by SEQ ID NO: 1; (b) an antibody, which is produced by a hybridoma whose accession number is FERM BP-7838, FERM BP-7839, FERM BP-7840, or FERM BP-8268; or (c) an antibody, which is competitive with the antibody produced by the hybridoma whose accession number is FERM BP-7838, FERM BP-7839, FERM BP-7840, or FERM BP-8268 upon binding with the polypeptide comprising the amino acid sequence represented by SEQ ID NO: 1. <IMAGE>