A photographing optical lens system includes six lens elements which are, 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. Each of the six lens elements has an object-side surface facing toward the object side and an image-side surface facing toward the image side. The first lens element has positive refractive power. The second lens element has negative refractive power. The sixth lens element has negative refractive power. At least one lens surface of at least one lens element of the photographing optical lens system has at least one critical point in an off-axis region thereof.