A cascade heat pump comprising: a first refrigerant cycle comprising a first compressor and a first indoor heat exchanger; a second refrigerant cycle comprising a second compressor and a second indoor heat exchanger; an outdoor heat exchanger in which a refrigerant compressed in the first compressor or the second compressor is condensed; a bypass tube allowing the refrigerant compressed in the second compressor to bypass the first compressor, thereby flowing into a discharge side of the first compressor; and a first flow rate regulating part disposed on a discharge side of the second compressor to introduce the refrigerant discharged from the second compressor into one of the first compressor and the bypass tube, characterized in that the cascade heat pump further comprises: a third refrigerant cycle disposed on a side of the first refrigerant cycle or the second refrigerant cycle, the third refrigerant cycle comprising a third compressor and a third indoor heat exchanger to perform a cooling or heating operation, a refrigerant heat exchanger in which the refrigerant discharged from the outdoor heat exchanger and the refrigerant circulating into the third refrigerant cycle are heat-exchanged with each other, and a further outdoor heat exchanger disposed on a side of the refrigerant heat exchanger to heat-exchange the refrigerant circulating into the third refrigerant cycle with external air; an equilibrium pressure tube extending from a discharge side of the first flow rate regulating part to the discharge side of the first compressor to allow the refrigerant to bypass the first compressor; and a second flow rate regulating part for adjusting an opened degree of the equilibrium pressure tube. a first refrigerant cycle comprising a first compressor and a first indoor heat exchanger; a second refrigerant cycle comprising a second compressor and a second indoor heat exchanger; an outdoor heat exchanger in which a refrigerant compressed in the first compressor or the second compressor is condensed; a bypass tube allowing the refrigerant compressed in the second compressor to bypass the first compressor, thereby flowing into a discharge side of the first compressor; and a first flow rate regulating part disposed on a discharge side of the second compressor to introduce the refrigerant discharged from the second compressor into one of the first compressor and the bypass tube, characterized in that the cascade heat pump further comprises: a third refrigerant cycle disposed on a side of the first refrigerant cycle or the second refrigerant cycle, the third refrigerant cycle comprising a third compressor and a third indoor heat exchanger to perform a cooling or heating operation, a refrigerant heat exchanger in which the refrigerant discharged from the outdoor heat exchanger and the refrigerant circulating into the third refrigerant cycle are heat-exchanged with each other, and a further outdoor heat exchanger disposed on a side of the refrigerant heat exchanger to heat-exchange the refrigerant circulating into the third refrigerant cycle with external air; an equilibrium pressure tube extending from a discharge side of the first flow rate regulating part to the discharge side of the first compressor to allow the refrigerant to bypass the first compressor; and a second flow rate regulating part for adjusting an opened degree of the equilibrium pressure tube. a third refrigerant cycle disposed on a side of the first refrigerant cycle or the second refrigerant cycle, the third refrigerant cycle comprising a third compressor and a third indoor heat exchanger to perform a cooling or heating operation, a refrigerant heat exchanger in which the refrigerant discharged from the outdoor heat exchanger and the refrigerant circulating into the third refrigerant cycle are heat-exchanged with each other, and a further outdoor heat exchanger disposed on a side of the refrigerant heat exchanger to heat-exchange the refrigerant circulating into the third refrigerant cycle with external air; a third compressor and a third indoor heat exchanger to perform a cooling or heating operation, a refrigerant heat exchanger in which the refrigerant discharged from the outdoor heat exchanger and the refrigerant circulating into the third refrigerant cycle are heat-exchanged with each other, and a further outdoor heat exchanger disposed on a side of the refrigerant heat exchanger to heat-exchange the refrigerant circulating into the third refrigerant cycle with external air; an equilibrium pressure tube extending from a discharge side of the first flow rate regulating part to the discharge side of the first compressor to allow the refrigerant to bypass the first compressor; and a second flow rate regulating part for adjusting an opened degree of the equilibrium pressure tube.