The invention relates to a flat wire and a manufacturing method thereof, wherein, the flat wire can be easily divided, and the divided flat wire and so on can be easily connected to a connector. The flat wire of the invention consists of (1) a plurality of parallel flat conductors with width of C and (2) an outer layer which is formed by extrusion of resins on the periphery of the flat conductors, coats the flat conductors and is provided with notches on positions with equal distance to respective coadjacent flat conductors, and the space P of the flat wire and the edge thickness M have the relationship of P equals to C plus 2 multiplied by M. The manufacturing method for the flat wire is as follows: firstly, a plurality of flat conductors with width of C are arranged according to the arrangement space P; secondly, the outer layer which is provided with the notches on the positions with equal distance to the respective coadjacent flat conductors and has the edge thickness of M equals to 1divided by 2multiplied by (P plus C) is formed by dies provided with approximately rectangular holes on one hand and extrusion of the coating resins on the periphery of the flat conductors on the other hand; thirdly, winding is performed.