A fire extinguishing system of an aircraft including a nozzle device that is provided on an installation member forming a compartment of the aircraft, wherein the nozzle device includes: a nozzle that is passed into an insertion hole formed in a nozzle installation section provided on the installation member, and discharges a fire extinguishing agent supplied from a supply source into the aircraft compartment; and a lid member that closes a gap between the nozzle and the nozzle installation section.