The invention detects quickly and with high precision abnormalities in
fuel cells. In a method of detecting abnormalities in a fuel cell 1
comprising a plurality of unit cells that generate power by supplying
hydrogen gas to an anode and supplying air to a cathode of each unit
cell, the abnormality in the fuel cell 1 is detected based on the speed
of the decrease in the cell voltages after stopping the fuel cell, i.e.,
after stopping the supply of the reacting gases to the fuel cell.