As an anti-tumor drug having an excellent anti-tumor effect and safety and also having an excellent therapeutic effect, an antibody-drug conjugate is provided, which is characterized in that an anti-tumor compound represented by formula (1) is linked to an anti-HER2 antibody through a linker having a structure represented by the formula: -L1-L2-LP-NH-(CH2)n1-La-(CH2)n2-C(=O)- (wherein the anti-HER2 antibody is linked at the terminal of L1, and the anti-tumor compound is linked to a carbonyl group in a -(CH2)n2-C(=O)- moiety wherein a nitrogen atom in an amino group located at position-1 in the anti-tumor compound serves as a linking part).
