The present invention provides a novel diazepine compound that blocks the I current or the Kv1.5 channel potently and more selectively than other K channels. The present invention relates to a diazepine compound represented by General Formula (1) or a salt thereof, wherein R, R, R, and Rare each independently hydrogen, lower alkyl, cyclo lower alkyl or lower alkoxy lower alkyl； R and R may be linked to form lower alkylene； A is lower alkylene optionally substituted with one or more substituents selected from the group consisting of hydroxyl and oxo； Y and Y are each independently -N= or -CH=； and R is group represented by (2) wherein R and R are each independently hydrogen or organic group； R and R may be linked to form a ring together with the neighboring group -X-N-X-； Xand X are each independently a bond, lower alkylene, etc.
