As an antitumor drug which is excellent in terms of antitumor effect and safety, there is provided an antibody-drug conjugate in which an antitumor compound represented by the following formula (I) is conjugated to an antibody via a linker having a structure represented by the following formula: -L 1 -L 2 -L P -NH-(CH 2 )n 1 -L a -L b -L c - or -L 1 -L 2 -L P - wherein the antibody is connected to the terminal of L 1 , the antitumor compound is connected to the terminal of L c or L P , and any one or two or more of linkers of L 1 , L 2 , and L P has a hydrophilic structure.
