S&P senior index analyst Howard Silverblatt said Apple is worth $604 billion, CNNMoney reported Friday.
Although it is the most valuable company in the world, its current value is just under the record of $618.9 billion, which was Microsoft's value in late December of 1999.
Microsoft's value has dropped. It is currently worth $260 billion.
But Microsoft's all-time record could soon fall, as Apple's largest money-maker by far is its iPhone and it is expected to launch the next generation iPhone in September.
A new iPad is also expected this year and the company's worth could increase with new developments in Apple's attempts to establish itself in the television industry.
The company's shares hit a record close on Thursday at $636.54 per share.
Its share price needs to reach $663.68 for Apple to become the most valuable company of all time, Silverblatt said.