A refrigeration air conditioning system having a moisture adsorption means regenerated by discharged condensation heat or other discharged heat of a low temperature range in the refrigeration cycle, and exerting stable cooling performance even at a dry-bulb temperature of 0° C. or less. A desiccant rotor, holds an adsorbent having pore sizes of, for example, 1-1.4 nm in a space at a predetermined temperature range of a dry-bulb temperature of 0° C. or less. Forming of frost on an evaporator is prevented by supplying the dehumidified air by the desiccant rotor to the evaporator disposed on a leeward side thereof in a freezing room as the desiccant rotor is rotated, while the adsorbent having adsorbed moisture is dried and recovers its adsorbing ability by supplying the air dried by discharged heat from a condenser on the windward side thereof to the desiccant rotor outside of the freezing room.