Provided is an image reading apparatus that can inhibit occurrence of a bright spot line image due to microstructures of a light guide. An image reading apparatus satisfies: 45−φ≦θ≦φ−ω/n (0≦ω≦ωmax); and 45−φ≦θ≦φ (−ωmax≦ω≦0), where θ is an angle (deg.) between a surface of original and a reflecting surface of a microstructure reflection surface of a light guide, ω is a half angle of view (deg.) of an imaging forming lens, ωmax (ωmax>0) is a maximum value (deg.) of the half angle of view of the imaging forming lens on an LED light source side with respect to a reading optical axis of the imaging lens, −ωmax is a maximum value (deg.) of the half angle of view of the imaging lens on a side opposite to the LED light source with respect to the reading optical axis, n is a refractive index of the light guide, and φ=sin−1(1/n).