NOVELTY - A printed circuit board (A1) (1) comprises insulating layer (2); conductor layer having a predetermined pattern and having first and second main surfaces and a side surface while being formed on insulating layer so that second main surface opposes the insulating layer; barrier layer formed on at least a partial region of first main surface and side surface of conductor layer and having higher corrosion resistance to acids than that of conductor layer; and conductive cover layer that covers the first main surface and side surface of conductor layer and barrier layer.    USE - As printed circuit board used in a fuel cell (claimed).    ADVANTAGE - The heterocyclic compound in the barrier layer increases the corrosion resistance to acids of the barrier layer. The barrier layer has a thickness of 1-1000 nm. In this case, the conductor layer can be sufficiently prevented from corroding. Adhesiveness between the conductor layer and the cover layer can be improved, and conductivity between the conductor layer and the cover layer can be improved. The cover layer including the resin improves the flexibility of the printed circuit board. In the printed circuit board, the by-product such as formic acid in the fuel cell is prevented from adhering to the conductor layer. Thus, the conductor layer is prevented from corroding. The contact resistance between the conductor layer and the cover layer is prevented from being increased. As a result, the electric power of the cell element in the fuel cell can be efficiently supplied to the exterior.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a fuel cell comprising a cell element, printed circuit board (A1), arranged as an electrode of the cell element, and a casing that accommodates the cell element and the printed circuit board; and    (2) manufacturing a printed circuit board involving forming a conductor layer having a predetermined pattern and having first and second main surfaces and a side surface on the insulating layer so that the second main surface opposes the insulating layer, and forming a barrier layer having higher corrosion resistance to acids than that of the conductor layer on at least a partial region of the first main surface and the side surface of conductor layer while forming a conductive cover layer that covers the first main surface and the side surface of conductor layer and barrier layer.    DESCRIPTION OF DRAWING(S) - The figure shows a plan view of the flexible printed circuit board.    Flexible printed circuit board (1)    Base insulating layer (2)    First insulating portion (2a)    Second insulating portion (2b)    Third insulating portion (2c)