NOVELTY - The method involves providing the fuel cell (3) with cathode side having a supply duct (5) to the cathode chamber (4) of the fuel cell. The cathode chamber of the fuel cell is provided with an exhaust line (7). The pressure on the cathode side is influenced through a pressure controller (19). The supply of gaseous medium in the area of ??the cathode side is varied so as to influence the pressure with the pressure controller. The air supply on the cathode side is varied through the pressure controller.    USE - Method for controlling pressure in fuel cell system mounted in vehicle (claimed).    ADVANTAGE - The pressure in fuel cell system can be controlled with a simple mechanical structure. The gaseous medium is supplied to influence the pressure, and the gas inflow into the region of the cathode side is increased or lowered according to cathode compartment of the fuel cell, in order to influence the pressure spreading in the entire cathode side. The pressure control can be realized very simply and efficiently over the change of supply of gaseous medium on the cathode side. The pressure control can be implemented easily and efficiently. The components can be implemented simply and inexpensively. The variation of the air supply enables simple and efficient pressure control of the fuel cell system. The fixed diaphragm or bungee cord with fixed geometry can be obtained, since the actual variation of the back pressure over increase or reduction of the volume is achieved by the influence of incineration. The coupled control circuits are accordingly coordinated with the pressure control process and can be compensated in such a way by the adjustment of moisture over air stoichiometry and the subsequent variation of pressure over the supply from fuel to burner.    DESCRIPTION OF DRAWING(S) - The drawings show the schematic views of the fuel cell system in vehicle.    Fuel cell (3)    Cathode chamber (4)    Supply duct (5)    Exhaust line (7)    Pressure controller (19)