PURPOSE: To eliminate contamination due to defrosted water, permit reusing as well as freezing of various configurations and improve the durability of cooling capacity by a method wherein highly water absorbing material is covered with a water-resisting and flexible sheathing sheet to manufacture the bag of ice by freezing it so as to have a required configuration under a condition that the highly water absorbing material has absorbed water in the degree of not saturated.

CONSTITUTION: When water is absorbed into highly water absorbing material 2 to the degree of not saturated by dipping the bag of ice into water or pouring water through the water permeating part of a sheathing sheet 1 and the bag is frozen under this condition, the water in the material 2 is frozen and solidified. In a stage, in which water is absorbed or water is frozen slightly before freezing, the water absorbing material 2 is soft and is deformable into any required configuration. Defrosted water is absorbed into the water absorbing material even if one part of ice is defrosted when frozen ice is used as refrigerant in such a manner whereby water will never flow out of the sheathing sheet 1. Further, cold water is held at the outside of the bag by retaining the water in the water absorbing material whereby the cooling capacity of the bag may be kept for a long period of time.