The present invention provides a novel amino compound that blocks the IKur current or the Kv1.5 channel potently and more selectively than other K+ channels. The present invention relates toa benzodiazepine compound represented by General Formula (1): or a salt thereof, wherein R 1 , R 2 , R 3 , and R 4 are each independently hydrogen or lower alkyl； R 2 and R 3 may be linked to form lower alkylene； A 1 is lower alkylene optionally substituted with one or more hydroxyls； and R 5 is an aryl or heterocyclic group, each of which is optionally substituted.
