An optical scanning device includes a housing, a light source that emits light, a rotatable polygon mirror that receives the light from the light source while rotating and deflects the light by reflecting the light in a direction corresponding to an angle of rotation thereof, a scanning optical system that guides the light from the rotatable polygon mirror to a scanning object in such a manner as to repeatedly scan the scanning object with the light, and an intermediate member that is provided between an optical member included in the scanning optical system and the housing. The intermediate member is connected to the optical member with rubber adhesive and is also connected to the housing with the rubber adhesive.