As an antitumor drug which is excellent in termsof antitumor effect and safety and has an excellenttherapeutic effect, there is provided an antibody-drugconjugate in which an antitumor compound represented loythe following formula is conjugated to an anti-HER2antibody via a linker having a structure represented bythe followingformula: -L1-L2-LP-NH-(CH 2)n1- La-(CH 2)n2-C(=O)- wherein the anti-HER2 antibody is connected tothe terminal L1, and the antitumor compound isconnected to the carbonyl group of the -(CH 2) n2-C(=O)-moiety with the nitrogen atom of the amino group atposition 1 as the connecting position.(see above formula)
