A method to control an FOD (flying on demand) voltage of a hard disk drive apparatus using a TA (thermal asperity) signal includes providing at least one protrusion having a predetermined height on a disk, moving a magnetic head to a position of the protrusion, and applying an FOD voltage for a test to the magnetic head, detecting the TA signal generated when the magnetic head touches the protrusion by the applied FOD voltage for a test, and determining the maximum FOD voltage, that is, the maximum FOD voltage applied to the magnetic head, based on the detected TA signal and determining an FOD voltage to control the FH (flying height) of the magnetic head based on the maximum FOD voltage.