A refrigerator comprising: a high-temperature evaporator for vaporizing a heat medium; a screw expander for converting the expansion force of the heat medium vaporized in said high-temperature evaporator to rotational force; a condenser to which the heat medium exhausted from said screw expander is introduced; a circulation pump for supplying at least a portion of the heat medium liquefied in said condenser to said high temperature evaporator; an expansion valve for decompressing the remaining portion of the heat medium liquefied in said condenser; a low-temperature evaporator for vaporizing the refrigerant decompressed by said expansion valve for heat absorption; a screw compressor for compressing the heat medium vaporized by said low-temperature evaporator; and a casing for housing said screw expander and said screw compressor, characterized in that said casing includes an intermediate space defined between a rotor chamber housing the screw expander and a rotor chamber housing the screw compressor wherein an exhaust passage of said screw expander and a discharge passage of said screw compressor are opened to the intermediate space in which the refrigerator is configured to introduce the heat medium discharged from said screw compressor while the heat medium merges with the heat medium exhausted from said screw expander, and wherein the intermediate space is connected to the condenser through a common flow passage; the exhaust side of a rotating shaft of said screw expander is connected to the discharge side of a rotating shaft of said screw compressor by a coupling within said intermediate space of said casing. a high-temperature evaporator for vaporizing a heat medium; a screw expander for converting the expansion force of the heat medium vaporized in said high-temperature evaporator to rotational force; a condenser to which the heat medium exhausted from said screw expander is introduced; a circulation pump for supplying at least a portion of the heat medium liquefied in said condenser to said high temperature evaporator; an expansion valve for decompressing the remaining portion of the heat medium liquefied in said condenser; a low-temperature evaporator for vaporizing the refrigerant decompressed by said expansion valve for heat absorption; a screw compressor for compressing the heat medium vaporized by said low-temperature evaporator; and a casing for housing said screw expander and said screw compressor, characterized in that said casing includes an intermediate space defined between a rotor chamber housing the screw expander and a rotor chamber housing the screw compressor wherein an exhaust passage of said screw expander and a discharge passage of said screw compressor are opened to the intermediate space in which the refrigerator is configured to introduce the heat medium discharged from said screw compressor while the heat medium merges with the heat medium exhausted from said screw expander, and wherein the intermediate space is connected to the condenser through a common flow passage; the exhaust side of a rotating shaft of said screw expander is connected to the discharge side of a rotating shaft of said screw compressor by a coupling within said intermediate space of said casing.