A backlight module and a display device are provided. The backlight module includes a light guide plate, a light source and a first prism film. The light guide plate includes a main body and plural oblique microstructures. The main body has a light-incident surface and at least one main surface connected to the light-incident surface. The main surface has a first area and a second area. The oblique microstructures are disposed in the first area. Each of the oblique microstructures has a first slope. A light source is disposed adjacent to the light-incident surface. The first prism film is disposed in front of the light guide plate. The first prism film has plural first prism microstructures. Each of the first prism microstructures has a second slope. One of the first slope and the second slope is a positive number, and the other one is a negative number.