In order to improve detecting accuracy in a gas leak detection for a fuel
cell, in a gas leak detection method for a fuel cell having a solid
polymer electrolyte membrane sandwiched by an anode and a cathode, an
output voltage is measured in an activated over-potential region in a
state in which the pressure of fuel gas which is supplied to the anode is
maintained higher than the pressure of gas which is supplied to the
cathode, and a gas leak is determined to exist when the output voltage is
lower than a predetermined pressure value.
