This invention relates to an agent for treating or inhibiting recurrence of acute myeloid leukemia and an agent for inhibiting growth of leukemia stem cells comprising a compound represented by formula (I) or a salt thereof: wherein Ar1 and Ar2 each represent aryl or heteroaryl; L represents O, S, NH, NHCO, or CONH; X represents CH or N; Y represents C1-3-alkylene; Z1 represents hydrogen, C1-6-alkyl, amino-C1-6-alkyl, C1-6-alkylamino-C1-6-alkyl, di(C1-6-alkyl)amino-C1-6-alkyl, hydroxy-C1-6-alkyl, C1-6-alkoxy-C1-6-alkyl, or carboxy-C1-6-alkyl; and Z2 represents C1-6-alkyl, amino-C1-6-alkyl, C1-6-alkylamino-C1-6-alkyl, di(C1-6-alkyl)amino-C1-6-alkyl, hydroxy-C1-6-alkyl, C1-6-alkoxy-C1-6-alkyl, or carboxy-C1-6-alkyl, Z1 and Z2 may, together with adjacent nitrogen, form a heterocyclic group containing as a ring member one or more hetero atoms, in addition to the nitrogen adjacent to Z1 and Z2.