A radiator includes a flat base (10), a pair of heat pipes (20) and a plurality of fins (30) on the base. The base defines a pair of grooves (12) through a top portion thereof. Each heat pipe includes parallel and symmetrical first and second sections (22, 24). The first sections are soldered to the base in the grooves. Each fin defines a notch (32) at a bottom portion thereof and a pair of holes (36) at opposite sides of the notch. Flanges (35) extend perpendicularly from the notches of the fins, cooperatively defining a streamline airflow guiding surface. Collars (37) extend perpendicularly from the holes of the fins, for receiving the second sections of the heat pipes.