A work chamber provided with a main case with the work space therein, an air supply unit for supplying air through an air supply filter provided at the upper front of the work space, a louver for guiding the air toward the back surface of the work space after passing through the air supply filter, and an illumination means provided at a position below the louver and in front of the louver. At least the surface of the louver that faces the illumination means is a reflective surface.
