PROBLEM TO BE SOLVED: To provide a coolant bag that can take in air into the bag if necessary and can discharge the air from the bag if not necessary, by using a structure capable of taking in and discharge the air from the coolant bag.SOLUTION: In the coolant bag, an agent A containing sodium 12 phosphate 2 water salt and sodium pyrophosphate 10 water salt is sealed in a first storage part, while an agent B containing a mixture of citric acid and ammonium salt is sealed in a second storage part, with the agent A and the agent B brought into contact with each other in use. The first storage part and the second storage part are formed by arranging a first surface film, a second surface film, and a bottom film in a superposed manner, with the periphery sealed, and with a partition seal installed that separates the first and second storage parts. In the first and second surface films, there are formed a plurality of ventilation holes respectively, where the ventilation holes of the first surface film and those of the second surface film are arranged so that their ventilation holes are not superimposed on each other.
