A backlight apparatus includes a guiding element and a light source disposed at one side of the guiding element. There is a plurality of reflective patterns at the bottom surface of the guiding element. Each reflective pattern is composed of at least one concavity and at least one convexity. The concavity is disposed at the rim around the convexity. As the light source emits light to the guiding element, the reflective area is increased by the concavity of the reflective pattern for increasing the reflecting effect and for distributing the brightness more uniformly, and thereby higher brightness and uniformity can be achieved.