A refrigerator comprising: a first refrigeration cycle unit that is configured to circulate a first refrigerant and includes a first compressor, a first condenser, a first expansion device, and a first evaporator; a second refrigeration cycle unit that is configured to circulate a second refrigerant and includes a second compressor, a second condenser, a second expansion device, and a second evaporator; a first valve unit installed at an outlet side of the first compressor or at an outlet side of the first condenser; and a first hot gas path connecting the first valve unit to the second evaporator and configured to supply the first refrigerant to the second evaporator, the first hot gas path extending from the first valve unit to an outlet side of the first condenser via the second evaporator, characterized in that the refrigerator further comprises: a third evaporator which is provided in the second refrigeration cycle unit and is connected to the second evaporator in series; a second valve unit disposed at an outlet side of the second condenser; a third valve unit disposed downstream of the second valve unit, being connected to an inlet side of the third evaporator; a second hot gas path (246, 346) configured to supply the second refrigerant having passed the second condenser to the third evaporator, the second hot gas path connecting the second valve unit and the third evaporator; a bypass path connecting the third valve unit and an outlet side of the third evaporator so as to allow the second refrigerant to bypass the third evaporator; and a combination part with which the bypass path is combined, the combination part being located in a pipe connecting the second evaporator and third evaporator. a first refrigeration cycle unit that is configured to circulate a first refrigerant and includes a first compressor, a first condenser, a first expansion device, and a first evaporator; a second refrigeration cycle unit that is configured to circulate a second refrigerant and includes a second compressor, a second condenser, a second expansion device, and a second evaporator; a first valve unit installed at an outlet side of the first compressor or at an outlet side of the first condenser; and a first hot gas path connecting the first valve unit to the second evaporator and configured to supply the first refrigerant to the second evaporator, the first hot gas path extending from the first valve unit to an outlet side of the first condenser via the second evaporator, characterized in that the refrigerator further comprises: a third evaporator which is provided in the second refrigeration cycle unit and is connected to the second evaporator in series; a second valve unit disposed at an outlet side of the second condenser; a third valve unit disposed downstream of the second valve unit, being connected to an inlet side of the third evaporator; a second hot gas path (246, 346) configured to supply the second refrigerant having passed the second condenser to the third evaporator, the second hot gas path connecting the second valve unit and the third evaporator; a bypass path connecting the third valve unit and an outlet side of the third evaporator so as to allow the second refrigerant to bypass the third evaporator; and a combination part with which the bypass path is combined, the combination part being located in a pipe connecting the second evaporator and third evaporator. a third evaporator which is provided in the second refrigeration cycle unit and is connected to the second evaporator in series; a second valve unit disposed at an outlet side of the second condenser; a third valve unit disposed downstream of the second valve unit, being connected to an inlet side of the third evaporator; a second hot gas path (246, 346) configured to supply the second refrigerant having passed the second condenser to the third evaporator, the second hot gas path connecting the second valve unit and the third evaporator; a bypass path connecting the third valve unit and an outlet side of the third evaporator so as to allow the second refrigerant to bypass the third evaporator; and a combination part with which the bypass path is combined, the combination part being located in a pipe connecting the second evaporator and third evaporator.