To obtain an ice making system and a low temperature storage system using it wherein power of a circulating pump and a condenser cooling fan, management of concentration of antifreeze, and an anticorrosion agent are dispensed with.

Connection is made in a sealed annular piping system by a natural convection type condenser 5 installed outdoors and exchanging heats to the outside air, an evaporator 9 installed in the water at a lower portion for heat exchange with water against the condenser 5, liquid piping 19 connecting a liquid coolant outlet 5a of the condenser 5 with a liquid coolant inlet 9a of the evaporator 9, and vapor piping 21 connecting a vapor coolant outlet 9b of the evaporator 9 with a vapor coolant inlet 5b of the condenser 5. Cooling medium is sealed in the sealed annular piping system so as to constitute a sealed freezing cycle. The liquid coolant obtained by condensing the vapor coolant by the condenser 5 under outside air temperature made to flow to the evaporator 9, and the vapor coolant evaporated in the evaporator 9 is naturally sucked into the condenser 5 of a low pressure, so as to circulate and work the cooking medium without power.