Apple has surpassed $US600 billion in value for the first time.
Apple shares reached a high of $US644 during trading on Tuesday, having crossed the $US500 threshold in February.
The BBC reports Apple's stock is up almost 60% since the start of the year.
It is another milestone for the iPhone maker, whose shares were worth as little as $US3.19 in 1997 when it faced the possibility of bankruptcy.
In March, the company said it will start paying a dividend to shareholders and to buy back some of its shares.
Apple's revival came about first in computers and then the iPod music player, which was followed by the iPhone and iPad.