A rail-vehicle ventilation system comprising: a ventilating section that ventilates air inside and outside a rail vehicle; a flow-rate adjusting section that adjusts a ventilation flow rate of ventilation by the ventilating section between a first ventilation flow rate and a second ventilation flow rate lower than the first ventilation flow rate; a control section that controls the flow-rate adjusting section; a vehicle-external-pressure information acquiring section that acquires vehicle-external-pressure information of the rail vehicle; and a vehicle-internal-pressure information acquiring section that acquires vehicle-internal-pressure information of the rail vehicle, wherein when it is determined that a difference between the vehicle-external-pressure information and the vehicle-internal-pressure information is within a tolerance range after the flow-rate adjusting section sets the ventilation flow rate to the second ventilation flow rate, the control section controls the flow-rate adjusting section to restore the ventilation flow rate to the first ventilation flow rate wherein the flow-rate adjusting section includes a connecting section connected to a duct through which air flows, and a valve operation section connected to the connecting section, and wherein the valve operation section includes a movable valve, an abutting edge against which the valve abuts, characterised in that either: packings are provided discretely over an entire circumference of the abutting edge with gaps between adjacent packings for flow of leaking air, or a small opening is formed through the valve for flow of leaking air. a ventilating section that ventilates air inside and outside a rail vehicle; a flow-rate adjusting section that adjusts a ventilation flow rate of ventilation by the ventilating section between a first ventilation flow rate and a second ventilation flow rate lower than the first ventilation flow rate; a control section that controls the flow-rate adjusting section; a vehicle-external-pressure information acquiring section that acquires vehicle-external-pressure information of the rail vehicle; and a vehicle-internal-pressure information acquiring section that acquires vehicle-internal-pressure information of the rail vehicle, wherein when it is determined that a difference between the vehicle-external-pressure information and the vehicle-internal-pressure information is within a tolerance range after the flow-rate adjusting section sets the ventilation flow rate to the second ventilation flow rate, the control section controls the flow-rate adjusting section to restore the ventilation flow rate to the first ventilation flow rate wherein the flow-rate adjusting section includes a connecting section connected to a duct through which air flows, and a valve operation section connected to the connecting section, and wherein the valve operation section includes a movable valve, an abutting edge against which the valve abuts, characterised in that either: packings are provided discretely over an entire circumference of the abutting edge with gaps between adjacent packings for flow of leaking air, or a small opening is formed through the valve for flow of leaking air.