An imaging optical lens assembly 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 first lens element with positive refractive power has a convex object-side surface. The second lens element has negative refractive power. The third lens element with refractive power has both an object-side surface and an image-side surface being aspheric. The fourth lens element with refractive power has both an object-side surface and an image-side surface being aspheric. The fifth lens element with refractive power has both an object-side surface and an image-side surface being aspheric. The sixth lens element with refractive power has both an object-side surface and an image-side surface being aspheric.