An arithmetic operation device for automobiles mounted on an automobile capable of automatic driving control, comprising: an arithmetic element; an arithmetic element state detection unit (111, 112) that detects a parameter indicating a state of the arithmetic element; an external device detection unit that detects a use state of an external device (104, 105) that affects the parameter from outside of the arithmetic element; a basic traveling function unit provided in the arithmetic element and configured to execute control related to a basic traveling function of the automobile; an automatic driving function unit provided in the arithmetic element and configured to execute control related to an automatic driving function of the automobile; and a mode selection unit provided in the arithmetic element and configured to select, based on a detection result of the arithmetic element state detection unit (111, 112) and a detection result of the external device detection unit, one of a normal mode in which both the basic traveling function unit and the automatic driving function unit are operated and a degeneration mode in which only the basic traveling function unit of the basic traveling function and the automatic driving function is operated, wherein the mode selection unit selects the degeneration mode when the parameter exceeds a threshold or when it is predicted that the parameter exceeds the threshold, characterized in that the parameter includes a voltage applied to the arithmetic element, the arithmetic element state detection unit includes a voltage detection section, and the mode selection unit selects the degeneration mode when an amplitude of the voltage applied to the arithmetic element is a predetermined amplitude or more or when it is predicted that the amplitude of the voltage applied to the arithmetic element is the predetermined amplitude or more, wherein the device includes an external communication device mounted on the automobile and configured to output information communicated with the outside of the automobile to the arithmetic element, and the mode selection unit predicts whether the amplitude of the voltage of the arithmetic element is the predetermined amplitude or more in consideration of a communication amount of the external communication device detected by the external device detection unit. an arithmetic element; an arithmetic element state detection unit (111, 112) that detects a parameter indicating a state of the arithmetic element; an external device detection unit that detects a use state of an external device (104, 105) that affects the parameter from outside of the arithmetic element; a basic traveling function unit provided in the arithmetic element and configured to execute control related to a basic traveling function of the automobile; an automatic driving function unit provided in the arithmetic element and configured to execute control related to an automatic driving function of the automobile; and a mode selection unit provided in the arithmetic element and configured to select, based on a detection result of the arithmetic element state detection unit (111, 112) and a detection result of the external device detection unit, one of a normal mode in which both the basic traveling function unit and the automatic driving function unit are operated and a degeneration mode in which only the basic traveling function unit of the basic traveling function and the automatic driving function is operated, wherein the mode selection unit selects the degeneration mode when the parameter exceeds a threshold or when it is predicted that the parameter exceeds the threshold, characterized in that the parameter includes a voltage applied to the arithmetic element, the arithmetic element state detection unit includes a voltage detection section, and the mode selection unit selects the degeneration mode when an amplitude of the voltage applied to the arithmetic element is a predetermined amplitude or more or when it is predicted that the amplitude of the voltage applied to the arithmetic element is the predetermined amplitude or more, wherein the device includes an external communication device mounted on the automobile and configured to output information communicated with the outside of the automobile to the arithmetic element, and the mode selection unit predicts whether the amplitude of the voltage of the arithmetic element is the predetermined amplitude or more in consideration of a communication amount of the external communication device detected by the external device detection unit.