A lens optical system includes first, second, third, and fourth lenses that are arranged between an object and an image sensor, in order from an object side, wherein the first lens has positive refractive power and an incident surface that is convex toward the object, the second lens has negative refractive power and both surfaces of which are concave, the third lens has positive refractive power and a meniscus shape that is convex toward the image sensor, and the fourth lens has negative refractive power and at least one of an incident surface and an exit surface of which is an aspherical surface, wherein the system satisfies the inequality, 3.0