1. An illumination device comprising:a light source for lighting up a desktop;
an arm mechanism incorporating a motor for moving a position of the light source;
a user camera that detects a user;
a desk camera that detects an illuminance distribution on the desktop;
an image processing part that calculates a posture of the user and a distance between a specific region of the user and the desk, based on a user image obtained with the user camera and a desk image obtained with the desk camera;
a computation part that calculates, based on the posture of the user derived with the image processing part and the illuminance distribution obtained with the desk camera, an optimal light source position of the light source at which dispersion of the illuminance distribution is minimized;
a warning part that generates a warning in a case where the distance is less than or equal to a predetermined value; and
an arm control part that operates the arm mechanism such that the light source moves to the optimal light source position.