PROBLEM TO BE SOLVED: To provide a composition for inhibiting cancer stem cells. SOLUTION: CDR 1H of SEQ ID NO:111, CDR2H of SEQ ID NO:114, CDR3H of SEQ ID NO:118, CDR1L of SEQ ID NO:119, CDR2L of SEQ ID NO:124, and SEQ ID NO:125. A pharmaceutical composition containing an anti-CD43 antibody or an antigen-binding fragment thereof, which comprises CDR3L of. Preferably, the antigenic determinant site consists of an amino acid sequence selected from SEQ ID NOs: 131, 132, 133 and 134. [Selection diagram] Figure 1【課題】癌幹細胞阻害用組成物の提供。【解決手段】SEQ ID NO:111のCDR1H、SEQ ID NO:114のCDR2H、SEQ ID NO:118のCDR3H、SEQ ID NO:119のCDR1L、SEQ ID NO:124のCDR2L、及びSEQ ID NO:125のCDR3Lを含む、抗CD43抗体又はその抗原結合断片を含有する医薬組成物。好ましくは、抗原決定部位は、SEQ ID NO:131、132、133、及び134から選択されたアミノ酸配列からなる、医薬組成物。【選択図】図1