A flexible printed circuit board (PCB) for a light emitting diode backlight unit includes a flexible base film; a plurality of metal lines on a first surface of the flexible base film; a cover layer on the metal lines and covering a center portion of the first surface of the flexible base film; a first gold-plating pattern on the metal lines and at both ends of the first surface of the flexible base film; a metal pattern on a second surface of the flexible base film and including a first sub-pattern at one end of the second surface, a second sub-pattern at the other end of the second surface and a plurality of third-sub patterns between the first and second sub-patterns of the metal pattern; and a second gold-plating pattern on the metal pattern and including a fourth sub-pattern on the first sub-pattern, a fifth sub-pattern on the second sub-pattern, and a plurality of sixth-sub patterns each on the third sub-patterns, wherein a first groove between a first double-layered pattern of the first sub-pattern and the fourth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, a second groove between a third double-layered pattern of the second sub-pattern and the fifth sub-pattern and a second double-layered pattern of the third sub-pattern and the sixth sub-pattern, and a third groove between adjacent second double-layered patterns respectively expose a portion of the second surface of the flexible base film.