If your forced air HVAC system does not have return ducts or if the return in this room is too restrictive, then the return air must flow under the door to a hallway and down to the hallway HVAC intake. If you don't use this bedroom much, you might want to restrict the incoming air at the duct in this room and/or open wider the vents on other rooms to decrease the pressure in the a/c vents and balance the heating and cooling.
If you use this room a lot and need this amount of airflow in, you might consider cutting 1/4 inch off the bottom of the door to allow more flow out of the room. I installed new oak doors on the bedrooms in our house and I erred on the side of leaving the doors too close to the tile floor. This means I have to carefully balance the restriction louvers on the air ducts to avoid pressurizing a particular room.
If there is insufficient space under the door the room may become pressurized and if there is a bathroom off the bedroom you may lose conditioned air through the exhaust vent in the bathroom.
Edit: I now think from the comments and answers that a whole bedroom could not be pressurized enough to force any significant air out the bathroom vent.