PROBLEM TO BE SOLVED: To provide an antitumor drug having an excellent antitumor effect and safety. An antitumor compound represented by the following formula and an anti-HER2 antibody are prepared by the following formula: -L 1 -L 2 -L P -NH-(CH 2 )n 1 -L a -(CH 2 )n 2 An antibody-drug conjugate, which is bound via a linker having a structure represented by -C(=O)-. (Anti-HER2 antibody binds at the end of L 1 , and an antitumor compound uses the nitrogen atom of the amino group at the 1-position as the binding site, and the carbonyl group of -(CH 2 )n 2 -C(=O)- moiety Join to) [Selection diagram] None【課題】抗腫瘍効果と安全性面に優れる、抗腫瘍薬の提供。【解決手段】下式で示す抗腫瘍性化合物と抗ＨＥＲ２抗体とを、次式：-L１-L２-LＰ-NH-(CH2)n１-Lａ-(CH2)n２-C(=O)-で示される構造のリンカーを介して結合させたことを特徴とする抗体－薬物コンジュゲート。（抗ＨＥＲ２抗体はL１の末端において結合し、抗腫瘍性化合物は、１位のアミノ基の窒素原子を結合部位として、-(CH2)n２-C(=O)-部分のカルボニル基に結合する）【選択図】なし
