To improve image quality by correcting the characteristic of an infrared cut filter provided in an image forming lens, with a simple configuration, in an image reader.

The image reader reflects light emitted from an illumination unit 10 extending in a main scan direction Y by an original on a glass and receives the reflected light by an imaging element through the image forming lens. The illumination unit 10 includes a long shaped light guide body 11, a light source (LED 15) arranged at one end of the light guide body 11, and a light refraction part (prism 12) and a reflection member (sheet 13) arranged in the lower surface of the light guide body 11. The light made incident from one end of the light guide body 11 is reflected by the prism 12 and the reflection sheet 13, while being guided in the main scan direction Y in the light guide body 11, so that the original is irradiated with the light. The reflection sheet 13 is set so that the reflectance of the light on a long-wavelength side is gradually decreased as it goes from both ends of the light guide body 11 to the central part of the light guide body 11.