A therapeutic agent for metastatic brain tumor, which contains the following formula(In the formula, A represents the binding position to the antibody) The antibody-drug conjugate that the drug linker and antibody bind to through the thioether bond is used as an active ingredient； The treatment method is characterized by administering the antibody-drug conjugate to an individual in need of treatment for metastatic brain tumors.一種轉移性腦腫瘤之治療劑，其含有下式(式中，A係表示與抗體的結合位置)所示的藥物連接子(linker)與抗體藉由硫醚鍵而結合的抗體-藥物結合物作為有效成分；及/或一種轉移性腦腫瘤之治療方法，其特徵為對需要轉移性腦腫瘤之治療的個體投予該抗體-藥物結合物。
