As an anti-tumor drug having an excellent anti-tumor effect and excellent safety and also having an excellent therapeutic effect, an antibody-drug conjugate is provided, said conjugate being characterized by being produced by linking an anti-tumor compound represented by formula (1) to an anti-HER2 antibody through a linker having a structure represented by the formula: L1-L2-LP-NH-(CH2)n1-La-Lb-Lc- or the formula: -L1-L2-LP- (in the conjugate, the anti-HER2 antibody is bound at the terminal of L1, and the anti-tumor compound is bound at the terminal of Lc or LP wherein a nitrogen atom in an amino group located at position-1 in the anti-tumor compound serves as a binding site).
