As it is indwelling retention target ones A, when it possesses bigger data compression ratio, than liquid D it inserts sack 12 in retractable it is filled the liquid C which possesses the setting point of low temperature into outer container 11 from liquid, D solidifies outer container after is filled the space with 11 and medium sack 12, low temperature retention container 10 is closed airtight in the liquid D where cubic measure augments. And, cooling low temperature retention container 10, liquid it is temperature with C and liquid D the setting point, at the same time at retention temperature of low temperature, retention target ones A are retained from the setting point by atmospheric pressure of the liquid in retention target thing A.保存対象物Aを内在させると共に、液体Dより大きな圧縮率を有し、液体Dより低温の凝固点を有する液体Cを充満させた伸縮自在な中袋12を外容器11内に入れて、凝固すると体積が増加する液体Dで外容器11と中袋12との間の空間を充満させた後、低温保存容器10を密閉する。そして、低温保存容器10を冷却して、液体Cと液体Dとの凝固点との間の温度であり、且つ保存対象物A中の液体の大気圧での凝固点より低温の保存温度で、保存対象物Aを保存する。
