A photographing lens system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. The second lens element has positive refractive power. The third lens element has a concave image-side surface, wherein both object-side and image-side surfaces thereof are aspheric. The fourth lens element has a convex image-side surface, wherein both object-side and image-side surfaces thereof are aspheric. The fifth lens element has negative refractive power, wherein both object-side and image-side surfaces thereof are aspheric. The sixth lens element has a concave image-side surface, wherein both object-side and image-side surfaces thereof are aspheric, and at least one of the two surfaces thereof has at least one inflection point. The photographing lens system has a total of six lens elements.