A flexible circuit board comprises a polyimide insulating layer 5 with land access holes 3 and a conductor circuit layer 4 provided thereon, and is produced by coating one surface of a conductor circuit metal foil 1 side with a polyimide precursor varnish, which is dried to give a polyimide precursor layer 2, where the polyimide precursor layer 2 is provided with land access holes 3 by a photolithography process; the conductor circuit metal foil 1 is patterned by the subtractive process to form conductor circuit layer 4; and the polyimide precursor layer 4 is then imidated to form polyimide insulating layer 5.