Backlight module, stereo display apparatus, and beam splitting film

A beam splitting film including a light transmissive plate and a plurality of strip protrusion groups is provided. The light transmissive plate has a first surface and a second surface. The strip protrusion groups are disposed on the second surface. Each of the strip protrusion groups includes a first strip protrusion and a second strip protrusion. The first strip protrusion has a first strip surface and a second strip surface inclined relative to the second surface. The second strip protrusion has a third strip surface and a fourth strip surface inclined relative to the second surface. An average slope of the first strip surface is not equal to an average slope of the third strip surface. An average slope of the second strip surface is not equal to an average slope of the fourth strip surface. A backlight module and a stereo display apparatus are also provided.