The object is to provide an Fms-like tyrosine kinase 3 (FLT3) inhibitor useful as a therapeutic agent for acute myeloid leukemia (AML). A novel nitrogen-containing heterocyclic compound represented by the general formula [1] or a salt thereof is provided. The compound or a salt thereof of the present invention can be used as an active ingredient of a pharmaceutical composition for a treatment of a disease or condition relating to FLT3, such as acute myeloid leukemia (AML) and acute promyelocytic leukemia (APL).