A backlight module includes a light source and an integrated optical film. The integrated optical film includes a base, a brightness enhancement layer and a diffusion layer. The base has a first surface and a second surface opposite to each other. The brightness enhancement layer has a plurality of brightness enhancement columns and a plurality of diffusion particles. The brightness enhancement columns are disposed on the first surface. The diffusion particles are dispersed in the brightness enhancement columns. The diffusion layer has a plurality of granular patterns disposed on the second surface in an irregular arrangement. Light beams emitted from the light source pass through the diffusion layer, the base and the brightness enhancement layer in proper order.