The effect of salt addition on the supercooling properties of erythritol was investigated in an attempt to create a novel sugar alcohol type of latent heat storage material that has high thermal storage density and remains in a supercooled state at room temperature. The mechanism of the effect was also examined. Various cationic and anionic species having different valences were each added to erythritol, and their effects on supercooling properties were evaluated with crystallization temperature and supercooling retention time as indices. The supercooling retention mechanism was also investigated focused on the interaction between erythritol and each additive by NMR (Nuclear Magnetic Resonance) spectroscopy. It was found that erythritol additives containing monovalent anions are effective as supercooling stabilizers, and additives containing divalent anions are effective as supercooling inhibitors. It was also found that cationic species have a smaller influence than anionic species. Additives that include the acetate ion were found to be a capable of maintaining erythritol in a supercooled state at room temperature, and the improvement of supercooling retention was considered to be due to the interaction between the hydroxy group of erythritol and the acetate ion.