A cooling device is provided for cooling at least one computer component device in a main frame. The cooling device comprises a case and at least one fan assembly. The case is mounted adjacent to the computer component device, and is provided with at least one first opening communicating with air outside the main frame and at least one second opening facing the computer component device. The fan assembly is mounted in the case to suck the air outside the main frame through the first opening and directly ventilate the computer component device through the second opening.