An air conditioner ECU transmits a communication message in a format for controlling a stepper motor. Since a stepper motor and a DC motor are controlled by a communication message in respective predetermined formats, the DC motor cannot be controlled with the communication message transmitted by the air conditioner ECU. Therefore, the sub ECU relays the communication message transmitted by the air conditioner ECU and drives the actuator. The sub ECU converts the communication message transmitted by the air conditioner ECU into control information corresponding to a predetermined format of each actuator and drives each actuator based on the converted control information.