A heat-dissipating device is provided for generating primary airflow to dissipate heat generated by external heat sources as well as secondary airflow to dissipate heat generated from the interior of the heat-dissipating device. The heat-dissipating device includes a primary fan and a secondary fan coupled with a shaft of the primary fan. The secondary fan is rotated along the shaft to generate the secondary airflow and dissipate heat generated by the heat-dissipating device per se. Thus, the operation temperature of the heat-dissipating device can be lowered to increase its life span.