PURPOSE: To obtain a clean room large in inner effective volume by discharging the gas inside the clean room body to the outside, making use of the fire extinguishing gas introduction pipe of a fire extinguishing gas ejector.

CONSTITUTION: The fire extinguishing gas introduction pipe 12d of a fire extinguishing gas ejector 22 for transports gas for fire extinguishing and ejects it into a clean room when a fire occurs inside the clean room body 21. A fire extinguishing gas discharger 23 discharges the gas inside the clean room body 21, which includes the fire extinguishing gas ejected from the clean room body 21, out of the clean room body 21. It is constituted such that the fire extinguishing gas discharger 2 discharges the gas inside the clean room body 12 out of the clean room 21, making use of the fire extinguishing gas introduction pipe 12d of the fire extinguishing gas ejector 22. Thereby, the fire extinguishing gas discharge pipe of the fire extinguishing gas discharger for a clean room becomes needless, and the effective volume of the clean room body becomes large.