A subminiature imaging optical system includes a first lens including a first lens part having a convex object-side surface, a second lens part having an object-side surface in contact with an image-side surface of the first lens part, and a third lens part having an object-side surface in contact with an image-side surface of the second lens part and a concave image-side surface, about the optical axis; and a second lens including a fourth lens part having an object-side surface with a convex center and a concave peripheral portion about the optical axis, a fifth lens part having an object-side surface in contact with an image-side surface of the fourth lens part, and a sixth lens part having an object-side surface in contact with an image-side surface of the fifth lens part, and an image-side surface with a concave center and a convex peripheral portion about the optical axis.