Disclosed are an optical member (100), a backlight assembly (500) and a liquid crystal display device (800) using the optical member. The optical member (100) includes an optical body (110) and a first fixing part (120). The optical body varies optical characteristic of first light incident into thereto to exit a second light. The first fixing part (120) is protruded from at least one side face of the optical body (110), and including a fixing hole (122) and a vibration attenuating means (124). The fixing hole (122) is elongated in a main expansion direction of the optical body (110), and the vibration attenuating means (124) is formed on an inner of the fixing hole to attenuate external vibration applied to the optical body (110). The fixing hole (122) allows movement of the optical member (100) in accordance with expansion of the optical member (100) caused by heat, thereby preventing wrinkles from being created on the optical body. The vibration attenuating member (124) prevents the optical body from being scratched.