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 R1, R2, R3, and R4 are each independently hydrogen or lower alkyl; R2 and R3 may be linked to form lower alkylene;A1 is lower alkylene optionally substituted with one or more hydroxyls; and R5 is an aryl or heterocyclic group, each of which is optionally substituted.