An image reading lens system of Example 1 includes six lenses having first to sixth lenses being arranged in order from an object side and an aperture diaphragm. In the image reading lens system, the first lens, the third lens, and the sixth lens are formed of negative lenses, and the second lens, the fourth lens, and the fifth lens are formed of positive lenses. The first lens, the second lens, the third lens, and the fifth lens are made of glass, and surfaces of all these lenses are formed of spherical surfaces. The fourth lens and the sixth lens are made of resin, and surfaces of the fourth lens and surfaces of the sixth lens are formed of aspheric surfaces. A cemented lens is formed of the second lens and the third lens with a cemented surface interposed therebetween, and is disposed adjacent to the aperture diaphragm.