A refrigerator, comprising: a cooling part for cooling an object to be cooled through heat exchange with a refrigerant (r); an expander-integrated compressor; and a refrigerant circulation line configured to circulate the refrigerant (r) through the expander-integrated compressor and the cooling part, wherein a low-stage compressor, a middle-stage compressor, and a high-stage compressor are disposed in series in the refrigerant circulation line, wherein the expander-integrated compressor includes: the middle-stage compressor; an expander for adiabatically expanding and cooling the refrigerant (r) discharged from the high-stage compressor; a first motor having an output shaft connected to the middle-stage compressor and to the expander; at least one non-contact type bearing (22, 24, 26), disposed between the middle-stage compressor and the expander, for supporting the output shaft of the first motor without being in contact with the output shaft; and a casing for housing the middle-stage compressor, the expander, and the at least one non-contact type bearing (22, 24, 26), wherein the refrigerator further comprises an extraction line disposed so as to communicate with a region (Is) between the middle-stage compressor and the expander in an interior space of the casing, and configured to extract at least a part of leaking refrigerant which flows from a side of the middle-stage compressor toward the expander inside the casing from the region (Is) to the refrigerant circulation line connected to an intake side or a discharge side of the middle-stage compressor outside the casing, and wherein the casing is configured to seal the region (Is) from outside of the casing so that at least a part of the leaking refrigerant via the extraction line is the only flow of the refrigerant (r) between the region (Is) and the outside of the casing. a cooling part for cooling an object to be cooled through heat exchange with a refrigerant (r); an expander-integrated compressor; and a refrigerant circulation line configured to circulate the refrigerant (r) through the expander-integrated compressor and the cooling part, wherein a low-stage compressor, a middle-stage compressor, and a high-stage compressor are disposed in series in the refrigerant circulation line, wherein the expander-integrated compressor includes: the middle-stage compressor; an expander for adiabatically expanding and cooling the refrigerant (r) discharged from the high-stage compressor; a first motor having an output shaft connected to the middle-stage compressor and to the expander; at least one non-contact type bearing (22, 24, 26), disposed between the middle-stage compressor and the expander, for supporting the output shaft of the first motor without being in contact with the output shaft; and a casing for housing the middle-stage compressor, the expander, and the at least one non-contact type bearing (22, 24, 26), wherein the refrigerator further comprises an extraction line disposed so as to communicate with a region (Is) between the middle-stage compressor and the expander in an interior space of the casing, and configured to extract at least a part of leaking refrigerant which flows from a side of the middle-stage compressor toward the expander inside the casing from the region (Is) to the refrigerant circulation line connected to an intake side or a discharge side of the middle-stage compressor outside the casing, and the middle-stage compressor; an expander for adiabatically expanding and cooling the refrigerant (r) discharged from the high-stage compressor; a first motor having an output shaft connected to the middle-stage compressor and to the expander; at least one non-contact type bearing (22, 24, 26), disposed between the middle-stage compressor and the expander, for supporting the output shaft of the first motor without being in contact with the output shaft; and a casing for housing the middle-stage compressor, the expander, and the at least one non-contact type bearing (22, 24, 26), wherein the refrigerator further comprises an extraction line disposed so as to communicate with a region (Is) between the middle-stage compressor and the expander in an interior space of the casing, and configured to extract at least a part of leaking refrigerant which flows from a side of the middle-stage compressor toward the expander inside the casing from the region (Is) to the refrigerant circulation line connected to an intake side or a discharge side of the middle-stage compressor outside the casing, and wherein the casing is configured to seal the region (Is) from outside of the casing so that at least a part of the leaking refrigerant via the extraction line is the only flow of the refrigerant (r) between the region (Is) and the outside of the casing.