A refrigeration system includes a compressor configured to compress a refrigerant, a condenser configured to condense the compressed refrigerant introduced from the compressor, a main flow passage configured to deliver the refrigerant compressed in the compressor to the condenser, a heat storage tank configured to partially store the heat of the refrigerant discharged from the compressor, an auxiliary flow passage configured to deliver the refrigerant compressed in the compressor to the heat storage tank, an expansion valve configured to expand the refrigerant condensed in the condenser, and an evaporation-side composite heat exchanger configured to evaporate the expanded refrigerant.