A backlight module and a display device are provided. The backlight module includes a light source structure and at least one optical film. The optical film is disposed above the light source structure. The optical film includes a main body and plural optical structures. The optical structures are disposed on the main body. Each of the optical structures is a tapered structure. Each of the optical structures has plural side surfaces, and a portion of light emitted from the light source structure is guided toward plural primary directions when passing through the side surfaces of the optical structures, and therefore the light emitted from the light source is no longer concentrated on the top of each of the optical structures.