To provide an anti-PAD4 antibody having excellent characteristics, and an excellent RA treatment method.SOLUTION: Provided are a polynucleotide or vector encoding an anti-PAD4 antibody that specifically binds to an epitope including positions 345, 347 and 348 of PAD4, and a method of producing anti-PAD4 antibodies comprising a step of growing cells in which is included the polynucleotide or vector, as well as a composition such as a citrullination activity inhibitor of PAD4 comprising the antibody or a pharmaceutical composition for treatment of RA or arthritis.SELECTED DRAWING: None【課題】優れた特性を有する抗PAD4抗体、又は優れたRAの治療方法の提供。【解決手段】PAD4の345、347、及び348位を含むエピトープに特異的に結合する抗PAD4抗体抗体をコードするポリヌクレオチド又はベクター、該ポリヌクレオチド又はベクターを含有する細胞を増殖させる工程を含む抗PAD4抗体の生産方法、並びに該抗体を含むPAD4のシトルリン化活性阻害剤、RA又は関節炎の治療用医薬組成物等の組成物。【選択図】なし