Provided is a method for determining the generation source of ripple voltage when abnormal ripple voltage is detected. The control device is for an electric compressor, the control device comprising: a detection unit that detects ripple voltage; a judgment unit that judges whether the ripple voltage is abnormal based on the value of the ripple voltage; and a cause determination unit that determines whether the cause of the abnormality is the electric compressor or some other external device, based on the control result of the electric compressor.
