Apparatus for diagnosing fault of fuel cell stack

Fault diagnosis apparatus to the failure diagnosis of the fuel cell stack, is connected to the fuel cell stack, is switched in accordance with the alternating signal applied to the fuel cell stack, the current flows alternating current suction unit with alternating current to generate an AC signal from the generating an AC signal supplied to the suction part comprises. It includes a stack of alternating current which current is inputted to the diagnostic processor as the suction portion sucked alternating current component from the fuel cell stack according to the AC signal.