A control device according to an aspect of the present disclosure includes: at least one memory configured to store instructions; and at least one processor configured to execute the instructions to: acquire an input image including an eye region that is a region of an eye part; estimate illuminance of the eye part from the acquired input image; and determine a light amount of illumination of visible light with which the eye part is irradiated in such a way that a pupil size of the eye part satisfies a size condition based on an illuminance size relationship that is a relationship between the illuminance and the pupil size.