Abstract: An ice thermal storage apparatus that uses ice as a thermal storage material, wherein without using a brine that is a heat transfer medium for chilling water to form ice, a thermal storage material in the form of an aqueous solution to which an additive is added so that supercooling can be secured stably is supercooled to the freezing point or below directly by a refrigerating apparatus, the supercooled aqueous solution is made into ice in the form of sherbet by a desupercooling apparatus over a thermal storage tank, and the remaining thermal storage material having the freezing temperature that has not been made into ice is sent again into the refrigerating apparatus to form a cycle so that ice can be formed in the thermal storage tank continuously.