Heat storage material composition, heat storage device, and heat storage method

A heat storage material composition contains a sugar alcohol and a stabilizer that allows the sugar alcohol to maintain a liquid state and a supercooled state. The stabilizer is one selected from (i) a salt that has a solubility of 9 g or more in 100 mL of 20° C. water and gives a monovalent anion, (ii) a polymer prepared by using the salt as a monomer, and (iii) a polymer having a molecular weight of 7,000 or more and 4,000,000 or less prepared by using, as a monomer, an alcohol having a solubility of 9 g or more in 100 mL of 20° C. water.