To use a general purpose air-conditioning amplifier unit matching with an air conditioner whole a dedicated monitor unit and a dedicated monitor control unit are used by separating the air conditioning amplifier unit from the monitor unit and the monitor control unit.

A monitor unit 10U is provided with a plurality of operation units 4 and the like outputting an operation command signal to an air conditioner 70A. In an air-conditioning amplifier unit 70U, an air conditioner control unit 70a controlling the air conditioner 70A is arranged, and between the air- conditioning amplifier unit 70U and a monitor control unit 80U, information is exchanged mutually via a harness 90. In this case, the air-conditioning amplifier unit 70U, the monitor unit 10U, and the monitor control unit 80U are separated from each other, so that a general purpose one matching with the on- vehicle air conditioner 70A can be used as the air-conditioning amplifier unit 70U while dedicated ones are used for the monitor unit 10U and the monitor control unit 80U.