To provide an easy coolant capable of easily mixing both by breaking a partition part separating both by external pressure, capable of maintaining a cooling effect over a long time, and capable of forming an instant coolant using inorganic metallic hydrate salt into a practical form in the instant coolant produced by mixing a substance exerting the endothermic action when dissolved in water and the inorganic metallic hydrate salt at use time.

This instant coolant 1 is formed by filling the substance exerting the endothermic action when dissolved in water in one chamber 5 of a sealed bag 2 composed of two chambers partitioned by an easily breaking partition part 4, and filling the inorganic metallic hydrate salt and its saturated aqueous solution in the other one chamber 6, and has a structure for mixing the inorganic metallic hydrate salt and its saturated aqueous solution with the substance exerting the endothermic action when dissolved in water by breaking the partition part 4 by the external pressure.