Depends on the setup of the room. If there is a wall to the left or right of the door, it should open in that direction. If there is no wall, it can open either way.

There are guidelines for which way a sliding door should open, but ultimately it depends on the specific situation and the preferences of the people using the door. In general, though, it's usually recommended that sliding doors open outwards so that they don't block access to the room when they're open.