 opened, supplying into the freezing store any gas suitable for the object-to-be-frozen such as a nitrogen gas to increase the inside gas pressure back to an atmospheric pressure level.  The quick freezing apparatus may further include a gas curtain unit provided near a door opening of the freezing store for producing a layered gas flow from the upper side toward the lower side, wherein the layered gas flow prevents the outside gas from mixing with the inside gas when the door is opened.  