An air conditioning device 100 comprises: a selecting means 31 for selecting a reverse defrost operating mode to stop heating operations and defrost all parallel heat exchangers 50 or a simultaneous heat and defrost operating mode to defrost each parallel heat exchanger 50 in order while continuing heat operations; and a determining means 32 for determining whether to start defrost operations. The determining means 32 is configured to start defrost operations in a state when the amount of frost formed on the parallel heat exchanger 50 is less when the simultaneous heat and defrost operating mode is selected than when the reverse defrost operating mode is selected.
