An automatic fire extinguishing device is characterized in that it contains a pressure resistant container which includes an extinguishant and a pressurization agent inside, a container valve attached to an opening of the pressure resistant container, a fire detection tube connected to the container valve, the fire detection tube equipped with a tubular base layer and a gas barrier layer laminated coaxially with the tubular base resin layer, the tubular base resin layer which is comprising thermoplastic resin, the gas barrier layer consisting of ethylene-vinyl alcohol copolymer resin (EVOH resin),
- wherein a thickness of the gas barrier layer is within a range from 0.005 mm to 0.1 mm and a thickness of the tubular base resin layer is within a range from 1 mm to 2 mm.