To provide an image reading apparatus and an image forming apparatus capable of efficiently, inexpensively and positively suppressing reading failure of the density of an original document due to a flare phenomenon without deteriorating an illumination light quantity in the reading position of the original document.

The image reading apparatus 4 for reading an image formed on an original document surface D is provided with a light source 8 for irradiating the original document surface D with illumination lights L1, L2. In this apparatus, an optical element 15 in which an uneven surface for diffracting and reflecting the illumination lights L1, L2 is continuously formed in a predetermined direction is arranged between the light source 8 and the original document surface D.