PURPOSE: To simplify gas leakage test of a fuel cell and provide the fuel cell with high safety, long life, and high reliability.

CONSTITUTION: A unit cell 3 comprises an electrolyte layer 6, a fuel electrode 1 and an oxidizing agent electrode 2 arranged on each side of the electrolyte layer 6. A cell block 5 is constituted by stacking a plurality of unit cells 3 on a cooling plate 4 through a separator 7. An upper fastening plate 8 and a lower fastening plate 10 are arranged at an upper end and a lower end of the cell block 5. The side surface of the cell block 5 is covered with a testing manifold 9a. The upper fastening plate 8 is pressed against the cell block 5 with a fastening plate compressing press 11, and the testing manifold 9a is mounted on the side surface of the cell block 5 with a testing manifold compressing press. As a nitrogen gas supply means to the testing manifold 9a, a valve 19 is connected to a bomb 18 through a pouring pipe, and a pressure gauge 20 and a flow meter 21 are arranged on the way of the poring pipe.