A cooling air supplying booth apparatus for supplying cooling air to pieces of equipment in a rack unit includes a first frame and a plurality of plates. The first frame forms edges of a cuboid. The plates are fixed to the first frame and disposed at four of sides of the cuboid and form a cooling air moving path. A cooling plate includes at least one fan and is disposed at the bottom of the first frame opposite the top side of the first frame. Cooling air is supplied to the cooling air moving path through the fan, and supplied to the equipment through an outlet side in the cooling air supplying booth apparatus.