PURPOSE: To embody failure diagnosis of an air-conditioner easily and rapidly by connecting external read means to an outdoor control unit of the air- conditioner, and taking out operation data of an indoor control unit from the outdoor control unit.

CONSTITUTION: An indoor control unit 2 is connected with an outdoor control unit 1, and a control signal is delivered therebetween for controlling air conditioning operation. Thereupon, external readout means 6 is connected to the external control unit 1 for taking out the operation data of the indoor control unit 2. To the external readout means 6 there are connected means 61 for taking out operation data from memory means 21 of the indoor control unit 2 and means 62 for receiving the operation data. Further, in the outdoor control unit 1 there are disposed means 41, 42 each for transferring data to the indoor control unit 2 and the external readout means 6. Additionally, in the indoor control unit 12 there is disposed means 22 for transmitting data to the outdoor control unit 1.