2000 Lexus RX 300 Alternator sound

Hi there, my 2000 lexus rx 300 ran out of battery a week ago. I thought it was the battery's problem, but it turn out the belt on the alternator broke. That is the reason that the battery couldn't charge at all. Before the belt brakes, i occassionally heard squeeking sounds when i start the car, especially when i turn on the AC. But the sounds settled down after a while, so I just ignored it. The squeeking sound had got worst before the old alternator belt broke. NOW HERE IS THE REAL QUESTION I WANT TO ASK YOU FOR ADVICE. I start to hear the squeeking sound again even with the new alternator belt, it doesnt last long, maybe around 10 seconds. Should I change the alternator? or might be problem with other parts of the Vehicle.

Thanks,
Peter