To provide a preserving system capable of re-using vaporized nitrogen, and moreover, capable of always cooling the specimens at a predetermined temperature or lower. The preserving system comprising a cylinder and the preserving vessel which is supplied with liquid nitrogen from this cylinder, is provided with a Stirling refrigerator and a condensing chamber arranged outside of said preserving vessel, and the gas phase part of this condensing chamber is made to communicate with that of said preserving vessel and also the liquid phase part is made to communicate with that of said preserving vessel, and further the cooling part of said Stirling refrigerator is arranged in said condensing chamber, therefore, the nitrogen vaporized in the preserving vessel is cooled by the cooling part of the Stirling refrigerator in the condensing chamber and liquefied again, and so this liquid nitrogen can be reused for cooling the preserving vessel. Moreover, since the preserving vessel can be cooled by the liquid nitrogen when performing maintenance on the Stirling refrigerator, the specimens in the preserving vessel can always be cooled at a predetermined temperature or lower.