To obtain a refrigeration air conditioning system having a dehumidifying function by means of a moisture adsorption means, allowing the moisture adsorption means to be regenerated by use of 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 1, being a moisture adsorption means, is made to hold an adsorbent having pore sizes of 5 μm or less, more preferably 20 nm or less, and furthermore preferably 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 20d is prevented by supplying the air dehumidified by the desiccant rotor 1 to the evaporator 20d disposed on the leeward side thereof in a freezing room as the desiccant rotor 1 is rotated, while the adsorbent having adsorbed moisture is made dried and made to recover its adsorbing ability by supplying the air dried by discharged heat from a condenser 20b disposed on the windward side thereof to the desiccant rotor 1 at the outside of the freezing room.