An air conditioning apparatus comprising: an outdoor unit which comprises a compressor and an outdoor heat exchanger and through which a refrigerant is circulated; an indoor unit through which water is circulated; a heat exchanger in which the refrigerant and the water are heat-exchanged with each other; a high-pressure guide tube extending from a high-pressure gas tube of the outdoor unit so as to be connected to one side of the heat exchanger; a high-pressure valve installed in the high-pressure guide tube , the high-pressure valve being configured to be opened and closed; a low-pressure guide tube extending from a low-pressure gas tube of the outdoor unit so as to be combined with the high-pressure guide tube ; a low-pressure valve installed in the low-pressure guide tube , the low-pressure valve being configured to be opened and closed; a refrigerant tube having one end defining a refrigerant branch point , at which the high-pressure guide tube and the low-pressure guide tube are combined with each other, and the other end connected to a refrigerant passage of the heat exchanger; a liquid guide tube extending from a liquid tube of the outdoor unit so as to be connected to the other side of the heat exchanger; a flow valve installed in the liquid guide tube to control a flow rate of the refrigerant; a bypass tube configured to connect a bypass branch point of the high-pressure gas tube to a bypass combination point of the liquid guide tube to bypass a high-pressure refrigerant existing in the high-pressure guide tube to the liquid guide tube ; a bypass valve installed in the bypass tube ; and a controller controls operations of the high-pressure valve , the low-pressure valve , the flow valve , and the bypass valve . an outdoor unit which comprises a compressor and an outdoor heat exchanger and through which a refrigerant is circulated; an indoor unit through which water is circulated; a heat exchanger in which the refrigerant and the water are heat-exchanged with each other; a high-pressure guide tube extending from a high-pressure gas tube of the outdoor unit so as to be connected to one side of the heat exchanger; a high-pressure valve installed in the high-pressure guide tube , the high-pressure valve being configured to be opened and closed; a low-pressure guide tube extending from a low-pressure gas tube of the outdoor unit so as to be combined with the high-pressure guide tube ; a low-pressure valve installed in the low-pressure guide tube , the low-pressure valve being configured to be opened and closed; a refrigerant tube having one end defining a refrigerant branch point , at which the high-pressure guide tube and the low-pressure guide tube are combined with each other, and the other end connected to a refrigerant passage of the heat exchanger; a liquid guide tube extending from a liquid tube of the outdoor unit so as to be connected to the other side of the heat exchanger; a flow valve installed in the liquid guide tube to control a flow rate of the refrigerant; a bypass tube configured to connect a bypass branch point of the high-pressure gas tube to a bypass combination point of the liquid guide tube to bypass a high-pressure refrigerant existing in the high-pressure guide tube to the liquid guide tube ; a bypass valve installed in the bypass tube ; and a controller controls operations of the high-pressure valve , the low-pressure valve , the flow valve , and the bypass valve . <EOS>