The present invention includes, from the object side to the image plane side, an aperture stop with a predetermined diameter, a first lens with a positive refractive power and a bi-convex shape with convex surfaces facing the object side and the image plane side, a second lens being formed as a meniscus shape with a concave surface facing the object side having a negative refractive power, and a third lens being formed as a meniscus shape with a convex surface facing the object side having a positive refractive power. By having a positive refractive power for the first lens and third lens and a negative refractive power for the second lens, a suitable back focus can be maintained while reducing the total length of the lens system. The imaging lens is thin and compact and has superior optical properties suited for mobile cameras mounted in portable telephones and PDAs.