Abstract: An imaging lens includes, in order from an object side, a first lens with a positive refractive power having a biconvex shape; an aperture stop having a predetermined aperture diameter; a second lens with a positive refractive power having a concave surface on the object side, at least one of the object-side surface and an image-plane-side surface of the second lens being aspherical; and a third lens with a negative refractive power having a concave surface on the object side and an aspherical surface with an inflection point in an effective-diameter area on the image-plane side, whereby aberrations can be effectively corrected, the total length of the lens system can be reduced to reduce the overall size, in particular the thickness, and a shutter can be readily accommodated.