The present invention ensures explosion-proof performance without increasing the capacity for supplying nitrogen-enriched air in an aircraft fuel system having a ventilation function. An aircraft fuel system includes: fuel tanks; an NEA supply system; a left ventilation channel extending from a ventilation duct to a fuselage and leading into the tanks; and a right ventilation channel extending from a ventilation duct to the fuselage and leading into the tanks. The tank leading to the channel and the tank leading to the channel are separated by a central wall. The tanks communicate with each other through a fuel path, which allows, of fuel and gas, only the fuel to pass through, and float valves.