A lens optical system including first, second, third, fourth, and fifth lenses that are sequentially arranged between an object and an image sensor on which an image of the object is formed. The first lens may have a positive refractive power and may be biconvex. The second lens may have a negative refractive power and may have a meniscus shape that is convex toward the object. The third lens may have a positive refractive power. The fourth lens may have a positive refractive power and may have a meniscus shape that is convex toward the image sensor. The fifth lens may have a negative refractive power, and at least one of an incident surface and an exit surface of the fifth lens may be an aspherical surface.