PROBLEM TO BE SOLVED: To accurately and stably set the characteristics of emission light from a light source part.SOLUTION: A light irradiation device comprises: a light source part that emits light a first light receiving part that receives, of emission light from the light source, light in a first wavelength region a second light receiving part that receives, of the emission light, light in a second wavelength region on a longer wavelength side than the first wavelength region and a light source control part that controls the light source part according to the intensity of the light received by the first light receiving part and the intensity of the light received by the second light receiving part.SELECTED DRAWING: Figure 2【課題】光源部からの出射光の特性を高精度かつ安定的に設定する。【解決手段】光を出射する光源部と、前記光源部からの出射光のうち第1波長域の光を受光する第1受光部と、前記出射光のうち前記第1波長域よりも長波長側の第2波長域の光を受光する第2受光部と、前記第1受光部による受光強度と前記第2受光部による受光強度とに応じて前記光源部を制御する光源制御部とを具備する光照射装置。【選択図】図2
