(I) An antibody-drug conjugate in which a drug linker represented by the following formula (where A indicates a binding position with an antibody) and an antibody are bound by a thioether bond, (ii) a histidine buffer, and (iii) sucrose. Alternatively, a pharmaceutical composition containing trehalose and (iv) a surfactant, and a method for freeze-drying the pharmaceutical composition.（ｉ）下式（式中、Ａは抗体との結合位置を示す）で示される薬物リンカーと抗体とがチオエーテル結合によって結合した抗体－薬物コンジュゲート、（ｉｉ）ヒスチジン緩衝剤、（ｉｉｉ）スクロース又はトレハロース、及び、（ｉｖ）界面活性剤、を含む医薬組成物、並びに該医薬組成物の凍結乾燥方法。
