[Problem] The subject of the present invention is to provide: an antibody with high internalization activity that specifically binds to CDH6, an antibody-drug conjugate with high antitumor activity containing the antibody, and the antibody-drug conjugate using the antibody-drug conjugate Drugs that have therapeutic effects on tumors, and tumor treatment methods using the antibodies, antibody-drug conjugates or drugs.[Solution] Provided by the present invention: an anti-CDH6 antibody with internalization activity, an anti-CDH6 antibody-drug conjugate showing high anti-tumor activity that combines the anti-CDH6 antibody and a novel PBD derivative, and medicines using these Products and tumor treatment methods.[課題]本發明之課題為提供：具有會對於CDH6特異性地結合之高內化活性的抗體、包含該抗體之具有高抗腫瘤活性的抗體-藥物結合物、使用了該抗體-藥物結合物的具有對腫瘤之治療效果的醫藥品、及使用了該抗體、抗體-藥物結合物或醫藥品的腫瘤之治療方法等。[解決手段]藉由本發明而提供：具有內化活性之抗CDH6抗體，結合了該抗CDH6抗體與新穎PBD衍生物之顯示高抗腫瘤活性的抗CDH6抗體-藥物結合物、使用此等的醫藥品及腫瘤之治療方法。
