An imaging lens apparatus comprises four lenses with refractive power by which lead the light from the object side to the image side: a first lens with a convex object-side surface and positive refractive power, at least one surface of the first lens is aspheric; an aperture stop set next to the first lens; a second lens which is a biconcave lens with negative refractive power, at least one surface of the second lens is aspheric; a third lens which is a positive meniscus lens with a concave object-side surface, both side of the third lens are aspheric; and a fourth lens which is a negative meniscus lens with a convex object-side surface, both side of the fourth lens are aspheric with at least one inflection point; and the imaging lens apparatus satisfy the conditions below: |1/slope_S8|>0.9; −0.2