A heat-dissipating device and a housing thereof. The housing includes a passage for guiding an air stream flowing from an opening to another opening, wherein an inner wall of the passage at at least one of the opening sides extends radially outwards with a rotational axis of the heat-dissipating device or the passage so as to enlarge intake or discharge area for the air streams. Accordingly, the intake airflow rate may be greatly increased and the heat-dissipating efficiency of the heat-dissipating device may be greatly enhanced without changing assembling conditions with other elements.