A heat sink includes a plurality of fins parallel to each other, and one heat pipe extending through these fins. A flow channel is formed between each pair of neighboring fins for channeling an airflow generated by an electric fan. A guiding member having a curved shape is arranged around the through hole for guiding the airflow flowing to the heat pipe. A space formed and surrounded by the guiding member is a tapered space, which narrows gradually along the direction of the airflow so as to guide the airflow flowing to the heat pipe.