Provided are: a light source that emits light; a light guide including: a curved portion including a light incident surface from which the light from the light source enters; and a linear portion including a light emission surface from which the light is emitted to an original, the linear portion coupled to the curved portion and extended in a main-scan direction, the curved portion reflecting the light entered from the light incident surface to the linear portion; and a frame that houses the light source, and the light guide, wherein the light guide includes an inclined portion inclined in a direction that increases an incident angle β of the light, the inclined portion formed in a range of the linear portion where the light reflected by the curved portion enters.