A refrigerator of the present invention includes a Rankine cycle heat engine and a refrigeration cycle heat engine which share a condenser, and drives a compressor of the refrigeration cycle by an expander of the Rankine cycle. A screw expander and a screw compressor are set up within a common casing, and the exhaust side of a rotating shaft of the screw expander is connected to the discharge side of a rotating shaft of the screw compressor. Preferably, an intermediate space in which an exhaust passage of the screw expander and a discharge passage of the screw compressor are merged together and connected to a condenser, and a coupling which connects the rotating shaft of the screw expander to the rotating shaft of the screw compressor is housed is formed within the casing.