The present invention relates to a ventilating system and ventilating system control method. A controller sets a static pressure setting value based on the airflow of the system as a whole, calculated from the airflow of venturi air valves of fume hoods that are operating, and controls the speed of rotation of a fan based on the static pressure setting value and the static pressure within a main duct. Doing so enables control of the speed of rotation of the fan to be performed while ensuring the airflow of the ventilating system, thus making it possible to prevent wasted motive force of the fan, even when the airflows of each of the venturi air valves are not identical and even when the changes in resistance of the branched duct system relative to the various changes in airflow are not identical, with the result that it is possible to advance energy conservation.