A mirror angle measurement and a servo control apparatus for a Holographic Digital Data Storage (HDDS) system is disclosed. The mirror angle measurement apparatus includes a first mirror having a first reflecting surface by which the reference beam is reflected toward the holographic medium, and a second reflecting surface by which a control beam is reflected to adjust the incident angle of the reference beam; a transmission unit for causing control beam to the second reflecting surface; a second mirror for returning the control beam to the second reflecting surface; and a photo detector unit for detecting the amounts of the control beam. The angle of the first mirror is adjusted based on a comparison result between the amounts of the control beam detected by the photo detector unit.