NOVELTY - The printed circuit board useful in a fuel cell e.g. cell phone battery, comprises an insulating layer (2), a conductor layer (3) that is provided on the insulating layer and has a predetermined pattern, and a coating layer that includes carbon and coats a surface of the conductor layer. The coating layer includes a resin composition having carbon. The insulating layer has a surface, where first and second regions of the insulating layer are adjacent to each other and a third region of the surface is adjacent to the first region.    USE - The flexible printed circuit board is useful in a fuel cell e.g. cell phone battery.    ADVANTAGE - The flexible printed circuit board prevents corrosion of the conductor layer without inhibiting a collecting action of the conductor layer thus improving reliability of connection between the fuel cell and external circuits.    DETAILED DESCRIPTION - The printed circuit board useful in a fuel cell e.g. cell phone battery, comprises an insulating layer (2), a conductor layer (3) that is provided on the insulating layer and has a predetermined pattern, and a coating layer that includes carbon and coats a surface of the conductor layer. The coating layer includes a resin composition having carbon. The insulating layer has a surface, where first and second regions of the insulating layer are adjacent to each other and a third region of the surface is adjacent to the first region. The insulating layer bends along a portion between the first and second regions such that the regions face each other. The conductor layer includes first (4a) and second (4b) conductor portions formed in the first and second regions of the insulating layer respectively, where the portions are formed to extend from the first and second conductor portions respectively to reach the third region of the insulating layer. The coating layer includes first and second coating portions that coat the first and second conductor portions and the first and second extraction portions respectively. First and second through holes are formed to penetrate the first and second regions of the insulating layer and first and second conductor portions of the conductor layer respectively. An INDEPENDENT CLAIM is included for a fuel cell.    DESCRIPTION OF DRAWING(S) - The diagram shows a view of flexible printed circuit board.    Flexible printed circuit board (1)    Insulating layer (2)    Conductor layer (3)    First conductor portion (4a)    Second conductor portion. (4b)