A refrigeration apparatus provided with: a multistage compression mechanism in which one low-stage compression part and a plurality of high-stage compression parts (22, 23, 24) respectively are connected in series; a heat-source-side main heat exchanger configured to function as a radiator during the cooling operation, and function as an evaporator during the heating operation; a plurality of heat-source-side sub heat exchangers configured to, during the cooling operation, function as radiators that cool intermediate-pressure refrigerant in the course of compression that is taken into the high-stage compression parts; a usage-side heat exchanger configured to function as an evaporator during the cooling operation and function as a radiator during the heating operation; switching mechanisms configured to change conditions so that during the cooling operation, the refrigerant is delivered from the heat-source-side main heat exchanger to the usage-side heat exchanger, and during the heating operation, the refrigerant is delivered from the usage-side heat exchanger to the heat-source-side main heat exchanger; an expansion mechanism configured to, during the cooling operation, depressurize the refrigerant delivered from the heat-source-side main heat exchanger to the usage-side heat exchanger, and during the heating operation, depressurize the refrigerant delivered from the usage-side heat exchanger to the heat-source-side main heat exchanger, a control part connected to the switching mechanism, the multistage compression mechanism and the expansion mechanism, and configured to perform each control operation during the cooling and the heating operation, characterized in that the plurality of heat-source-side sub heat exchangers is further configured to, during the heating operation, function as evaporators, the switching mechanisms is further configured to change conditions so that during the heating operation, the refrigerant is further delivered from the usage-side heat exchanger to the heat-source-side sub heat exchangers, the expansion mechanism is further configured to, during the heating operation, depressurize the refrigerant delivered from the usage-side heat exchanger to the heat-source-side sub heat exchangers, and the refrigeration apparatus is further provided with a refrigerant piping group, that connects the multistage compression mechanism, the switching mechanisms, the heat-source-side main heat exchanger, the heat-source-side sub heat exchangers, the expansion mechanism and the usage-side heat exchanger, so that during the heating operation, the refrigerant flows in series to not less than two of the heat-source-side sub heat exchangers from among the plurality of heat-source-side sub heat exchangers configured to function as the evaporators. a multistage compression mechanism in which one low-stage compression part and a plurality of high-stage compression parts (22, 23, 24) respectively are connected in series; a heat-source-side main heat exchanger configured to function as a radiator during the cooling operation, and function as an evaporator during the heating operation; a plurality of heat-source-side sub heat exchangers configured to, during the cooling operation, function as radiators that cool intermediate-pressure refrigerant in the course of compression that is taken into the high-stage compression parts; a usage-side heat exchanger configured to function as an evaporator during the cooling operation and function as a radiator during the heating operation; switching mechanisms configured to change conditions so that during the cooling operation, the refrigerant is delivered from the heat-source-side main heat exchanger to the usage-side heat exchanger, and during the heating operation, the refrigerant is delivered from the usage-side heat exchanger to the heat-source-side main heat exchanger; an expansion mechanism configured to, during the cooling operation, depressurize the refrigerant delivered from the heat-source-side main heat exchanger to the usage-side heat exchanger, and during the heating operation, depressurize the refrigerant delivered from the usage-side heat exchanger to the heat-source-side main heat exchanger, a control part connected to the switching mechanism, the multistage compression mechanism and the expansion mechanism, and configured to perform each control operation during the cooling and the heating operation, characterized in that the plurality of heat-source-side sub heat exchangers is further configured to, during the heating operation, function as evaporators, the switching mechanisms is further configured to change conditions so that during the heating operation, the refrigerant is further delivered from the usage-side heat exchanger to the heat-source-side sub heat exchangers, the expansion mechanism is further configured to, during the heating operation, depressurize the refrigerant delivered from the usage-side heat exchanger to the heat-source-side sub heat exchangers, and the refrigeration apparatus is further provided with a refrigerant piping group, that connects the multistage compression mechanism, the switching mechanisms, the heat-source-side main heat exchanger, the heat-source-side sub heat exchangers, the expansion mechanism and the usage-side heat exchanger, so that during the heating operation, the refrigerant flows in series to not less than two of the heat-source-side sub heat exchangers from among the plurality of heat-source-side sub heat exchangers configured to function as the evaporators.