In an aspect of the present invention, each of plural control units which controls drive of an electric actuator diagnoses existence of abnormality in drive control of the electric actuator, the abnormality differing from control unit to control unit; the control unit transmits diagnostic result thereof to another control unit; the control unit outputs an abnormal determination signal as a signal indicating diagnostic result therefrom when at least one of the diagnostic result thereof and the diagnostic result of another control unit indicates abnormality; and the control unit transfers the drive control of the electric actuator to an abnormal use control state when the abnormal determination signal is output from at least one of the plural control units.