Provided is a plug connector having an insulator and a plug connector fixing bracket that is hard to collapse (break). A plug connector (15) is attachable to and detachable from a receptacle connector (35) and includes: a plug insulator having an outer wall that includes a pair of longitudinal walls and a pair of transverse walls together constituting an annular projection engageable with an engagement recess of the receptacle connector (35); a plug contact group arranged in a row and supported by the longitudinal wall of the outer peripheral wall, contacts a receptacle contact group when the annular projection is fit into the engagement recess, and is connected to a circuit pattern of a plug side circuit board; and a plug connector fixing bracket mounted on the transverse walls. The plug connector fixing bracket includes a receiving surface facing a bottom surface of the transverse walls, a transverse outer wall and a transverse inner wall that bend from the receiving surface and respectively extend along an inner surface and an outer surface of the transverse walls, and a pair of longitudinal outer walls that bends from the receiving surface and extends along outer surfaces of the longitudinal walls.