Provided are: a dibenzooxepin derivative represented by general formula (I) [wherein Y represents a hydrogen atom or the like RA represents a hydrogen atom or the like X represents a group represented by formula (b3) (wherein RB represents a hydrogen atom or the like) or the like A represents a group represented by formula (a18) (wherein R1 represents a hydrogen atom or the like and RC and RD are the same as or different from each other and independently represent a hydrogen atom or the like) or the like] or a pharmaceutically acceptable salt thereof, which has a PPAR? agonistic activity and the like and is useful as, for example, a therapeutic agent and/or a prophylactic agent for type-2 diabetes or the like and others.本發明提供一種具有PPARγ激動活性等,而用作2型糖尿病等之治療劑及/或預防劑等之以下述通式(I)[式中,Y表示氫原子等;RA表示氫原子等;X表示式(b3)(式中,RB表示氫原子等)等;A表示式(a18)(式中,R1表示氫原子等;RC及RD相同或不同,表示氫原子等)等]所表示的二苯并氧呯衍生物或其藥學上所容許之鹽等。
