A heat radiating unit in the form of a heat sink includes a contact section arranged on a central portion of an end face of the heat sink for contacting with a heat source, and having more than one extension plate outward extended therefrom; a first heat-dissipating section composed of multiple curved radiation fins outward extended from two opposite sides of the contact section to provided increased heat radiating areas; and a second heat-dissipating section composed of multiple straight fins outward extended from another two opposite sides of the contact section and outer surfaces of the extension plates. The contact section conducts heat generated by the heat source to the first and second heat-dissipating sections, through which airflow produced by a cooling fan flows to carry the heat away from the heat sink in multiple directions to achieve enhanced heat-dissipating effect.