NOVELTY - A fuel cell system (1) comprises fuel cell; compressor (31) for supplying oxidant gas to the fuel cell, having first rotational speed region and second rotational speed region; and compressor controlling units for controlling the compressor by calculating a command rotational speed for commanding the compressor based on required amount of power generation.    USE - As fuel cell system (claimed) such as polymer electrolyte fuel cell (PEFC). Also useful in fuel cell vehicle e.g. two-wheeled motor vehicle, train, and ship, domestic or commercial stationary fuel cell systems; and used in a water heater system.    ADVANTAGE - The fuel cell system suppresses noise and vibration of a compressor.    DETAILED DESCRIPTION - A fuel cell system (1) comprises a fuel cell; a compressor (31) for supplying an oxidant gas to the fuel cell, having a first rotational speed region within rotational speed increases, a noise becomes greater than predetermined value, and a second rotational speed region within the rotational speed increases, the noise becomes equal to or less than the predetermined value; and a compressor controlling units for controlling the compressor by calculating a command rotational speed for commanding the compressor based on a required amount of power generation, where the compressor controlling units prohibits the compressor from rotating at a rotational speed within the first rotational speed region, and when the command rotational speed within the first rotational speed region is calculated, the command rotational speed is changed to a rotational speed within the second rotational speed region which is above the first rotational speed region, or the command rotational speed is changed to a rotational speed within the second rotational speed region which is below the first rotational speed region.    DESCRIPTION OF DRAWING(S) - The figure shows block diagram of fuel cell system.    Fuel cell system (1)    Fuel cell stack (10)    Flow paths (12)    Compressor (31)    Accelerator pedal (51)