An image reading device including an illumination unit that has a light guide body guiding light of a light source that is facing one longitudinal end surface of the light guide body to an object to be read; and an image forming optical device that is parallel to the light guide body, has a lens array with an incidence surface in which lens surfaces are arranged in the longitudinal direction of the light guide body, and condenses reflected light from the object which is incident on the incidence surface, thereby forming an erect equal-magnification image on a sensor. The image reading device further includes a frame on which is disposed the image forming optical device. A second frame projects in a direction away from the first frame and connects to the first frame, or the frame connects to an H-shaped cross-section frame.