A flexible circuit board with high connection reliability and a manufacturing method thereof, wherein the flexible circuit board has a bent section formed thereon, can be deformed flexibly, and wherein a wiring layer will not be peeled off or ruptured even when deformation is repeated onto the flexible circuit board, heat is radiated from electronic parts, or minute wiring is formed on the flexible circuit board. The flexible circuit board is provided with an insulating film comprised of liquid crystal polymer, a wiring layer formed upon the insulating film, and an insulating layer comprised of liquid crystal polymer formed upon the wiring layer. The flexible circuit board has a bent section with a radius of curvature of R (mm) formed on at least one location thereof, and is made to be deformable in a state with the radius of curvature of the bent section maintained at R (mm).