A light irradiation system for irradiating light to an irradiation area extending in a main scanning direction of a document face when placed on an image scanning apparatus includes a light source; a light guiding member to guide light emitted from the light source; and a reflector to reflect a part of light exiting from the light guiding member to the document face. The irradiation area is irradiated by the reflection light reflected by the reflector and a direct light exiting from the light guiding member without reflection at the reflector. The light guiding member includes an incidence surface where the light from the light source enters; and an exit surface where the light entered from the incidence surface exits. The reflector is disposed at a position in a direction that light intensity of light emitting from the light source becomes the strongest.