Abstract: A light irradiation device includes a tube including a tube main body and a light emitting portion, a plurality of wiring boards disposed inside the light emitting portion and including a plurality of light emitting elements disposed at an equal interval mounted, an anode lead wire for connecting an anode terminal of each of the wiring boards to a power source, and a cathode lead wire for connecting a cathode terminal of each of the wiring boards to the power source. In the light emitting portion, a central lumen and surrounding lumens that are arrayed at a 90° interval around the central lumen are formed. The wiring boards are disposed in the respective surrounding lumens with the light emitting elements arrayed along a longitudinal direction of the light emitting portion.