A dibenzoxepin derivative represented by the following general formula (I) wherein Y is a hydrogen atom and the like, RA is a hydrogen atom and the like, X is the formula (b3) wherein RB is a hydrogen atom and the like, and the like, A is the formula (a18) wherein R1 is a hydrogen atom and the like, and RC and RD are the same or different and each is a hydrogen atom and the like, and the like, which has a PPARγ agonist activity and the like, and useful as a therapeutic agent and/or prophylaxis agent and the like for type 2 diabetes and the like, or a pharmaceutically acceptable salt thereof and the like is provided.
