An air conditioning apparatus comprises a single heat source device including a compressor, a reversing valve, an outdoor heat exchanger and an accumulator; a plurality of indoor units including indoor heat exchangers and first flow controllers; a first main pipe and a second main pipe for connecting between the heat source device and the indoor units, the first main pipe having a greater diameter than the second main pipe, a first branch joint which can selectively connect one end of the indoor heat exchanger of each indoor unit to either one of the first main pipe and the second main pipe; a second branch joint which is connected to the other end of the indoor heat exchanger of each indoor unit through the first flow controllers, and which is also connected to the second main pipe through a second flow controller; the first branch joint and the second branch joint being connected together through the second flow controller; a junction device which includes the first branch joint, the second flow controller and the second branch joint, and which is interposed between the heat source device and the indoor units; and a valve which is provided between the first main pipe and the second main pipe in the heat source device, and which can selectively switch the side of the first main pipe to lower pressure and the side of the second main pipe to higher pressure.