The disclosure relates to a light irradiation device which can improve curability of photo-curable materials. A light irradiation device includes a first supply section having a porous portion, the first supply section being capable of supplying a gas to a photo-curable material through the porous portion; and an irradiation section disposed in alignment with the porous portion or disposed downstream from the porous portion, the irradiation section being capable of irradiating the photo-curable material with light.