A motor-driven throttle valve control device for an automobile having an auto-drive function for keeping a running speed of the automobile constant, including a throttle shaft for opening and closing a throttle valve by a rotation thereof; a spring for rotating the throttle shaft in a direction to open the throttle valve; a limiter for limiting a maximum opening angle of the throttle shaft against a biasing force of the spring; a first operating device for rotating the limiter around the throttle shaft in response to an operational amount of depression of an accelerator device of the automobile; a second operating device for limiting an opening angle of the throttle shaft within a range between the maximum opening angle defined by the limiter and a full closed angle of the throttle valve; a motor for rotating the second operating device around the throttle shaft; a third operating device for opening the throttle shaft beyond the maximum opening angle defined by the limiter; and a connecting device for connecting the third operating device to the motor while the auto-drive function of the automobile is activated; whereby an opening angle of the throttle shaft is adjusted by the motor within the range equal to or less than the maximum rotating angle defined by the operational amount of the accelerator device while the auto-drive function is not activated, and an opening angle of the throttle shaft is adjusted by the motor irrespective of the operational amount of the accelerator device so as to keep the running speed of the automobile constant while the auto-drive function is activated.