The shifting stock market briefly made Amazon chief Jeff Bezos the world's richest man this week.

Stock in the e-commerce company hit an all-time high on Thursday, but by Friday morning, Microsoft founder Bill Gates had reclaimed the lead.

Mr Bezos owns about 80 million shares, or 17 per cent, of Amazon. His shares were valued at more than $US90 billion during the brief peak.

Mr Bezos also owns The Washington Post.

Mr Bezos' net worth was about $US90.6 billion when the market opened on Thursday, while Mr Gates had just $US90.1 billion.

But Mr Gates would still be the undisputed leader if he did not keeping giving away billions of dollars away to philanthropic causes.

Amazon shares fell in after-markets trading as the company reported net income of $US197 million, or 40 cents per share, in the second quarter, down from $US857 million, or $US1.78 per share, a year ago.

Revenue grew 25 per cent to $US38 billion.

The current Forbes Top 10 list;

  • Bill Gates — Microsoft
  • Jeff Bezos — Amazon
  • Amancio Ortega — Zara
  • Warren Buffet — Berkshire Hathaway
  • Mark Zuckerberg — Facebook
  • Carlos Slim Helu — Telecom (Mexico)
  • Larry Ellison — software mogul
  • Michael Bloomberg — Bloomberg LP
  • Berard Arnault — LVMP
  • The Koch Brothers