1. An illumination device comprising:a light source for lighting up a desktop;
an arm mechanism that moves a position of the light source;
an illuminance distribution detection means that detects an illuminance distribution on the desktop;
a computation part that calculates a light source position at which illuminance unevenness decreases, based on the illuminance distribution on the desktop detected by the illuminance distribution detection means; and
an arm control part that operates the arm mechanism such that the light source moves to the light source position calculated by the computation part.