PURPOSE: To make it possible to preserve fish in the state of raw fish having appearance, taste, etc. thereof for several days and rationalize transportation, preservation, etc., by filling and packing fillets of the landed raw fish with a mixed gas of CO2 and N2, and preserving the packaged fillets at a low temperature.

CONSTITUTION: A fish, e.g. young yellowtail or sea bream, is usually bled, and the fish body is divided into three pieces of the upper and lower fillets and bones. The resultant fillets are then peeled or sliced and placed into a plastic film bag, etc., filled with a mixed gas of CO2 and N2 at 70W20:30W80% mixing ratio and sealed. The fillets or slices packaged in the bag filled with the gas are finally preserved at -1W+8°C.