A disk spacer coupled to an outer circumference of a hub of a spindle motor in a hard disk drive to support at least one data storage disk, wherein at least one groove generating flow of air toward an outer circumference of the disk is formed at an outer circumferential surface of the spacer. The groove is formed to be deeper from an arbitrary position on the outer circumferential surface of the spacer in a direction opposite to a rotation direction of the disk, and has a blade surface extending from the deepest position to the outer circumferential surface. The blade surface is substantially perpendicular to a tangential line at the outer circumferential surface of the spacer.