An image reading device to read an image carried on a document, including: an image reading section to read an image carried on a document; a polygonal member, mounted to face the image reading section, and spaced from the image reading section at a predetermined distance, the polygonal member includes a document feeding flat surface which faces the image reading section when the document is fed thereon, a white flat surface, and a black flat surface; a light source to emit light rays onto the image carried on the document, and onto the polygonal member when the document is not fed; and a control section to control an amount of the light rays emitted from the light source; wherein the control section corrects an amount of light rays concerning the white color and the black color, based on the amount of the light rays read by the image reading section.