A backlight module and a display device are provided. The display device includes a display panel and a backlight module. The backlight module includes a back plate, a spacer element, and an optical element. The spacer element passes through the back plate and includes a base portion, a supporting portion, a positioning portion and a first protruding portion. The base portion has a first surface and a second surface. The supporting portion is disposed on the first surface. The positioning portion is disposed on the second surface. The first protruding portion is disposed on the second surface and is located around the positioning portion. The first protruding portion has a third surface away from and parallel to the second surface. The optical element is disposed on the spacer element. A part of the back plate is located between the base portion and a part of the positioning portion.