To provide a lighting device which can read high-definition image information by reducing bright point generation in read image information.

A lighting device, which forms an image of image information of an original put on an original stand to a line sensor arranged in a main scanning direction through an imaging optical system and lights the image information used for an image reading device for obtaining the image information, has: a light source part wherein a plurality of point light sources are arranged in the main scanning direction; and a diffusion means which diffuses and transmits incident light along the major scanning direction disposed in an optical path connecting the light source part and an image reading position of the original. An optical flux region generated on an original reading surface of the original after optical flux from each point light source passes through the diffusion surface is long in the major scanning direction as compared with a sub-scanning direction, and is curved in the sub-scanning direction.