An air conditioning apparatus comprising: a four-way valve, a refrigeration cycle including a compressor, an indoor heat exchanger, a pressure reducer and an outdoor heat exchanger, that are connected to constitute a fluid circuit through which a cooling medium is circulated, the outdoor heat exchanger serving as an evaporator for evaporating the cooling medium in a case where a heating operation is performed and as a condenser for condensing the cooling medium in a case where a defrosting operation is performed; and an idle defrosting operation determining device including a temperature detecting device detecting a pipe temperature of the outdoor heat exchanger, characterized by a low temperature integrated value calculating means calculating a low temperature integrated value through a time-based summation or integration of a temperature difference between a freezing point temperature and the pipe temperature in a case where the pipe temperature, which is detected while the defrosting operation is carried out, falls within a temperature range from a predetermined low temperature lower than the freezing point temperature and the freezing point temperature, a high temperature integrated value calculating means calculating a high temperature integrated value through a time-based summation or integration of a temperature difference between the freezing point temperature and the pipe temperature in a case where the pipe temperature, which is detected while the defrosting operation is carried out, falls within a temperature range from a predetermined high temperature higher than the freezing point temperature and the freezing point, and a determining means determining whether or not the idle defrosting operation is carried out on the basis of a magnitude relationship between the calculated low temperature integrated value and the calculated high temperature integrated value. a four-way valve, a refrigeration cycle including a compressor, an indoor heat exchanger, a pressure reducer and an outdoor heat exchanger, that are connected to constitute a fluid circuit through which a cooling medium is circulated, the outdoor heat exchanger serving as an evaporator for evaporating the cooling medium in a case where a heating operation is performed and as a condenser for condensing the cooling medium in a case where a defrosting operation is performed; and an idle defrosting operation determining device including a temperature detecting device detecting a pipe temperature of the outdoor heat exchanger, characterized by a low temperature integrated value calculating means calculating a low temperature integrated value through a time-based summation or integration of a temperature difference between a freezing point temperature and the pipe temperature in a case where the pipe temperature, which is detected while the defrosting operation is carried out, falls within a temperature range from a predetermined low temperature lower than the freezing point temperature and the freezing point temperature, a high temperature integrated value calculating means calculating a high temperature integrated value through a time-based summation or integration of a temperature difference between the freezing point temperature and the pipe temperature in a case where the pipe temperature, which is detected while the defrosting operation is carried out, falls within a temperature range from a predetermined high temperature higher than the freezing point temperature and the freezing point, and a determining means determining whether or not the idle defrosting operation is carried out on the basis of a magnitude relationship between the calculated low temperature integrated value and the calculated high temperature integrated value.