An air conditioning apparatus comprising:
   a single heat source device (A) including a compressor (1), a reversing valve (2), an outdoor heat exchanger (3) and an accumulator (4);
   a plurality of indoor units (B,C,D) including indoor heat exchangers (5) and first flow controllers (9);
   a first main pipe (6) and a second main pipe (7) for connecting between the heat source device (A) and the indoor units (B,C,D);
   a first branch joint (10) which can selectively connect one end of the indoor heat exchanger (5) of each indoor unit (B,C,D) to either one of the first main pipe (6) and the second main pipe (7);
   a second branch joint (11) which is connected to the other end of the indoor heat exchanger (5) of each indoor unit (B,C,D) through the first flow controllers (9), and which connects the other end to the second main pipe (7) through a second flow controller (13);
   the first branch joint (10) and the second branch joint (11) connected together through the second flow controller (13);
   the second branch joint (11) connected to the first main pipe (6) through a third flow controller (15);
   a junction device (E) which includes the first branch joint (10), the second flow controller (13), the third flow controller (15) and the second branch joint (11), and which is interposed between the heat source device (A) and the indoor units (B,C,D);
   the first main pipe (6) having a greater diameter than the second main pipe (7); and
   a switching arrangement (40) which can be arranged between the first main pipe (6) and the second main pipe (7) in the heat source device (A) to switch the first main pipe (6) and the second main pipe (7) to a low pressure side and to a high pressure side, respectively, when the outdoor heat exchanger (3) works as a condenser or as an evaporator; characterized in that it comprises:
   a first timer (61) for changing the setting of the second flow controller (13) at a first cycle during operation of the compressor (1);
   a second timer for returning the setting of the second flow controller (13) to its initial setting at a second cycle longer than the first cycle; and
   determination means (63) for changing the setting of the second flow controller (13) by a predetermined value at a time based on outputs from the first timer (61), and for returning the setting of the second flow controller (13) to the initial setting based on an output from the second timer (62).