A single focus wide-angle lens module includes a fixed aperture diaphragm, a first, a second, a third and a forth lens arranged from an object side to an image side in the following sequence: the first lens, the fixed aperture diaphragm, the second lens, the third lens and the forth lens. The first lens has a negative refractive power, a concave surface toward the image side, and at least one aspheric surface. The second lens has a positive refractive power and a concave surface toward the object side, and said second lens is made of glass. Further, the third lens has a meniscus shape, a positive refractive power, a concave surface toward the object side, and at least one aspheric surface. The fourth lens has a positive refractive power, a convex surface toward the object side, and at least one aspheric surface.