Florida billionaire William Koch placed the winning bid in person at Brian Lebel's annual Old West Auction in Denver.
The 130-year-old tintype image had been expected to sell for between £188,000 ($300,000) and £250,000 ($400,000).
Mr Koch, an energy company boss, said after the auction that he planned to allow several museums to display the photo.
The photograph was taken outside a saloon in Fort Sumner, New Mexico, in late 1879.
It shows the notorrious outlaw gripping the upright barrel of a Winchester carbine, with a Colt 45 pistol strapped to his hip.