A gas injection device a placement portion on which a first or second container is placed, an ejection portion which is placed on the placement portion and ejects a purge gas, and a sealing portion protruding from the placement portion so as to surround a periphery of the ejection portion. The ejection portion, with the purge gas being injected into an inlet of the second container, does not come in contact with the inlet. The sealing portion, with the purge gas being injected into an inlet of the FOUP, does not impede the contact between the ejection portion and the inlet.