An air conditioner comprising: an air-conditioning control unit that controls air-conditioning running based on running information that is action information during running and operation setting information; a data read and write unit to which a storage medium configured to store therein data can be removably connected, and that can write running information and operation setting information transmitted from the air-conditioning control unit in the storage medium during air-conditioning running and can read running information and operation setting information stored in the storage medium before stop of running, from the storage medium when restarting air-conditioning running; a data control unit that transfers the running information and the operation setting information transmitted from the air-conditioning control unit to the data read and write unit to be written in the storage medium, or transfers, to the air-conditioning control unit, the running information and the operation setting information stored in the storage medium before stop of running and read from the storage medium by the data read and write unit; an operation unit that can input the operation setting information for performing an operation of the air-conditioning running; and characterised by comprising a communication unit that performs transmission and reception of data between the data control unit and the data read and write unit in a bidirectional manner, wherein the air-conditioning control unit automatically transmits the running information and the operation setting information to the data control unit on a regular basis, the data control unit stores the running information and the operation setting information received from the air-conditioning control unit in a storage file together with storage-date information, and then transmits the storage file to the data read and write unit via the communication unit, and the data read and write unit receives the storage file from the data control unit and writes the received file in the storage medium. an air-conditioning control unit that controls air-conditioning running based on running information that is action information during running and operation setting information; a data read and write unit to which a storage medium configured to store therein data can be removably connected, and that can write running information and operation setting information transmitted from the air-conditioning control unit in the storage medium during air-conditioning running and can read running information and operation setting information stored in the storage medium before stop of running, from the storage medium when restarting air-conditioning running; a data control unit that transfers the running information and the operation setting information transmitted from the air-conditioning control unit to the data read and write unit to be written in the storage medium, or transfers, to the air-conditioning control unit, the running information and the operation setting information stored in the storage medium before stop of running and read from the storage medium by the data read and write unit; an operation unit that can input the operation setting information for performing an operation of the air-conditioning running; and characterised by comprising a communication unit that performs transmission and reception of data between the data control unit and the data read and write unit in a bidirectional manner, wherein the air-conditioning control unit automatically transmits the running information and the operation setting information to the data control unit on a regular basis, the data control unit stores the running information and the operation setting information received from the air-conditioning control unit in a storage file together with storage-date information, and then transmits the storage file to the data read and write unit via the communication unit, and the data read and write unit receives the storage file from the data control unit and writes the received file in the storage medium.