Provides a light irradiation apparatus having a configuration as possible efficient cooling of the member to be disposed in the light transmission region in which the LED of the light transmission. Light irradiation device, surrounds the plurality of light emitting devices, light transmission area through which light is passed through a cooling mechanism, a plurality of light emitting elements disposed on the back surface of the substrate and cooling the substrate and the plurality of light emitting elements disposed on a surface of the substrate, receiving the inner wall, the substrate, the plurality of the light emitting element, a cooling mechanism and an inner wall arranged to also and at the same time, the air inlet for introducing air to the back surface of the substrate in the housing, the light transmission region to create a space between the inner wall, the back surface of the substrate the passage, and the air inlet and the flow passage connecting the space, and air in the space is provided with a circulation port disposed to be out of a light passage area, the cooling mechanism comprises cooling the air introduced into the air inlet, and the light transmission region and the air and the convection in the space between the.