A disclosed optical scanning device includes: a plurality of light beam irradiation devices irradiating a light beam; a deflector deflecting the plural light beams irradiated from the light beam irradiation devices into substantially opposite directions; scanning optical systems disposed substantially in an opposing manner relative to the deflector as a center, the scanning optical systems each scanning a scanning surface using the light beam deflected by the deflector; and at least one light screening material screening a flare light emitted from a first scanning lens in the scanning optical system so as to prevent the flare light from being projected onto a second scanning lens in the substantially opposite scanning optical system. The light screening material screening the flare light emitted from the first scanning lens is disposed more closely to the second scanning lens than to the first scanning lens.