NOVELTY - A fuel cell system comprises a fuel cell stack (10) having several unit cells producing electricity; a switching unit (20) connecting several unit cells to a discharge resistor; a switching controller (30) synchronously operated when the voltage of the fuel cell stack reaches an open circuit voltage after power generation of the fuel cell stack is stopped; and a sensing unit (40) sensing respective cell voltages of unit cells and generating cell voltage sensing signals to control activation periods of the select control signals.    USE - As a fuel cell system (claimed) for generating electricity.    ADVANTAGE - The fuel cell system lowers the cathode level of a fuel cell stack within a short period of time after the operation of the fuel cell system is stopped.    DETAILED DESCRIPTION - A fuel cell system comprises a fuel cell stack (10) having several unit cells producing electricity; a switching unit (20) connecting several unit cells to a discharge resistor; a switching controller (30) synchronously operated when the voltage of the fuel cell stack reaches an open circuit voltage after power generation of the fuel cell stack is stopped, where the switching controller generating select control signals to control the switching unit; and a sensing unit (40) sensing respective cell voltages of unit cells and generating cell voltage sensing signals to control activation periods of the select control signals. The switching unit comprises first discharge switches; and second discharge switches. An INDEPENDENT CLAIM is included for operating a fuel cell system involving activating the select control signals when the voltage of the fuel cell stack reaches an open circuit voltage after the power generation of the fuel cell stack is stopped; and connecting the unit cells to the discharge resistor whenever the select control signals are activated.    DESCRIPTION OF DRAWING(S) - The figure shows view of circuit diagram of a fuel cell system.    Fuel cell stack (10)    Switching unit (20)    Switching controller (30)    Sensing unit (40)