Short amounts of time lying on their tummies is good for babies' physical development. It lets them learn how to move their head, limbs and neck.
It can also be a good time to talk to them, so they hear plenty of words. If you talk to them and praise them throughout, it can help soothe them through what can be a stressful time for your baby.
Remember - babies should only ever be placed on their tummies when they're awake and you're in the room with them.