A cover member including an air guiding portion and an HDD including the cover member are provided. The HDD includes: a housing including a base member and a cover member; a spindle motor installed on the base member; a data storage disk mounted on the spindle motor; and an actuator rotatably installed on the base member, and including a read/write head for recording data onto the disk or reproducing data recorded on the disk. The cover member includes an air guiding portion protruding from a bottom surface of the cover member toward a surface of a data storage disk to guide an air flow generated by a rotation of the disk to the outside of the disk, and the air guiding portion has a width that changes along a rotating direction of the disk. Therefore, the air flow generated by the rotation of the disk can be guided outside of the disk by the air guiding portion formed on the cover member, and the air flows fast, and thus, the particles on the disk can be discharged outside of the disk efficiently.