PROBLEM TO BE SOLVED: To provide an antibody binding to a TM4SF20 protein and methods for the diagnosis and treatment of cancer using the antibody.SOLUTION: The present invention provides an anti-TM4SF20 antibody, and a pharmaceutical composition and a diagnostic drug comprising the antibody as an active ingredient and useful in the treatment and diagnosis of TM4SF20-expressing cancer such as stomach cancer, lung adenocarcinoma, pancreatic cancer, and colon cancer. The present invention provides an antibody having antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC). The present invention provides an antibody comprising a heavy chain variable region comprising a specific amino acid sequence and a light chain variable region comprising a specific amino acid sequence.【課題】TM4SF20タンパク質に結合する抗体、及び前記抗体を利用した癌の診断と治療方法の提供。【解決手段】抗TM4SF20抗体、及び前記抗体を有効成分とする、胃癌、肺腺癌、膵臓癌、大腸癌等のTM4SF20を発現する癌の治療及び診断に有用である医薬組成物及び診断薬。抗体依存性細胞傷害活性細胞障害性（ADCC活性）又は補体依存性細胞傷害活性（CDC活性）を有する抗体。特定のアミノ酸配列を有する重鎖可変領域又は特定のアミノ酸配列を有する軽鎖可変領域を有する抗体。【選択図】なし
