A disk spacer located on a rotator of a spindle motor to allow an additional disk to be mounted on the spindle motor, the disk spacer including a screw hole formed in a central part of the disk spacer to allow a clamping screw to pass through, a first disk pressing part located in a lower surface of an outer circumference part of the disk spacer to press surroundings of a central hole of a first disk directly mounted on the rotator, and a second disk supporter located on an upper surface of the outer circumference part of the disk spacer to support surroundings of a central hole of a second disk located above the first disk, and a hard disk drive having the disk spacer.