A heat dissipating device includes a heat sink, and an adjusting member. The heat sink includes a base, and a plurality of fins formed on a top surface of the base. The adjusting member includes a mounting portion mounted to a side surface facing an airflow-generating source of the base, a first air-blocking portion connected to an upper portion of the mounting part, and a second air-blocking portion connected to a lower portion of the mounting part. Positions of the first air-blocking portion and the second air-blocking portion relative to the base are adjustable for adjusting distribution of an airflow on top and bottom sides of the base when the airflow flows through the heat dissipating device.