A light irradiation device according to the disclosure comprises: a light source comprising a plurality of light-emitting elements; a heat-dissipating member thermally connected to the light source; an air blower section capable of blowing air on the heat-dissipating member; a drive section which drives the light source; and a housing which receives therein the light source, the heat-dissipating member, the air blower section, and the drive section, the housing comprising a plurality of ventilating slots serving as inlets and outlets for outside air, a lower face provided with an irradiation opening for external irradiation of light from the light source, a side face which is vertically oriented, and an inclined face which is located on an upper side of the housing and is opposed to the lower face, and the inclined face is provided with at least one ventilating slot.